Tuesday, December 14, 2010

PH253 final grades, mark 2

After going through the whole spreadsheet and looking at the final exams a third time, I decided to revise upward the partial credit on a couple of questions on the final. This will affect a lot (but not all) of you, depending on whether you chose to do those problems or not, and depending on what exactly you did. For some of you, the change was enough to affect your final grade.

I also went through everyone's final exam for a third time, and on a couple of exams I found that I had misunderstood the answer given, and you were owed more points.

Long story short, some grades needed to be revised.* Once I check my spreadsheet for what must be the 15th time, I am going to upload really final grades later this evening. I've been obsessing about this for three days now, but I think finally have gone over everything enough that I think it is consistent and fair.

*I didn't revise anyone's grade downward. If there was a grading error in your favor, it stayed.

Monday, December 13, 2010

PH253: preliminary grades on myBama

I've posted "final" grades on myBama, subject to the following qualifications:
  1. I have to check my spreadsheet thoroughly to be sure all my calculations are correct.
  2. I will have one more look at your final exams if you are on the borderline between two grades (I've graded them twice thusfar).
  3. Some of you might still sneak in an extra-credit assignment or late HW by the end of Monday.  (HINT)
So, I may have to make revisions after I review everything again, but as of right now everything seems to be in order. If you feel there is a mistake, contact me ASAP. Ditto if you want to know your grade breakdown.

Overall, I think most of you will not be surprised by your grade - not many of you moved up or down greatly based on your final exam score. (The class average was 0.76% higher after the final, the final exam average was 82%.) Notably, however, a couple of you managed to pull out a passing grade based on a very impressive showing on the final, which was nice to see.

Anyway, I hope you enjoyed the semester, I certainly did.

Thursday, December 9, 2010

PH253 Final exam pro tip

Pro tip: a problem might look on first sight just like one you've seen, but you still have to read it all the way through to make sure.

I say that since I'm seeing that same mistake again & again on HW9 ... the second problem was nearly like one from last year, but the second part was different in a crucial way. By "different" I mean "not even remotely close."

Let's recap: when you see a familiar-looking problem tomorrow, it might be a trap. Make sure I haven't changed anything key before you just go solving stuff all willy-nilly.

And, a bonus pro-tip: don't forget your calculator. There may actually be numbers other than pi and 2 on the exam. I think a 7 got in there while I wasn't looking.

PH253: server issues

UPDATE 2: with the server being down, Moodle is also down until further notice. Hopefully it will come back up some time today. Also, a draft of the formula sheet for the final.

UPDATE: HW and Exams mirrored here. The additional notes as well (well, most of them, until I hit my quota on bama.edu. Lame.)

For what I hope to be a short while, old HW/exams/etc are unavailable, owing to some script kiddie messing with the server I'm using:
I just got word that the machine that runs the faculty websites has been hax0red, so we have to take it offline till we can figure out what happened.
I will try to get a mirror up later this morning.

PH253: HW10 solutions

I have HW10 solutions ready. Given the end-of-semester craziness, I know quite a few of you will turn HW10 in late and take the hit on points. That's fine by me, it is your choice.

Because of that constraint, I had planned to not post the HW10 solutions publicly, but give them out by email to anyone who had already turned in HW10. The idea was that you wouldn't get to see the solutions until I saw your completed HW set.

Of course, that idea was hopelessly naive, and probably just punishes the people who need the most help. 

So, here are the HW10 solutions. I will still accept HW10 up through the final exam, minus the usual late penalty. Remember that I drop the lowest homework.

PH253: 8am exams suck and we can't do a thing about it

So our exam is 8am this Friday. That really sucks, and there is nothing we can do about it. Here are some thoughts about surviving the exam:
  1. Sleep the night before. All-night cramming may help you learn a few new things, but on a problem-based exam it is critical that you are able to think clearly and quickly. Zoning out because you're tired works against that very strongly.
  2. Use a buddy system if you're not a morning person. Seriously. Two different times I have actually called students on their cell phone to get them out of bed after the exam started. Call each other in the morning so you don't oversleep.
  3. Don't bother memorizing stuff. I want to see if you can think & solve problems, so you'll have all the formulas you need.
  4. Do ask questions during the exam. If it isn't 100% clear to you, ask for clarification. I may or may not be able to answer your question, but it can't hurt.
  5. Do be explicit about showing your work, and turn in anything you wrote on. Partial credit is key. If you are stuck on how to finish a problem, at least describe in words what you would like to do, that's worth something.
  6. Try not to get stuck on any one problem, since you will be somewhat pressed for time. (You will have more than enough time to finish if you work carefully and quickly, but if you get stuck for 15min on one problem, that may not be the case).
  7. Use your formula sheets for example problems, notes to yourself, or a guide to what various formulas are for (and what they are not for). You'll have a sufficient formula sheet, but that only helps if you recognize the formulas ...
  8. Remember that Wolfram Integrator will not be there to save the day on the exam, so remind yourself how to integrate the hard way ;-) Anything beyond basic polynomials will be on the formula sheet.
As I have more random work-avoiding thoughts, I will post them here ...

Wednesday, December 8, 2010

PH253: Exam 2 solutions

Just realized today after one of you emailed me that I never posted Exam 2 and its solution.

Here you are. Let me know if you find any errors or need further clarification on any problems.

Also, last semester's final with solutions.

PH253: final exam

I've decided to make it easier on you for the final, at least in terms of what you need to study.

The final exam questions will be drawn entirely from exam and homework problems from this and last semester, including last semester's final exam. (Just like I did for the last exam.) All I'm going to do is take old HW and exam problems, change some quantities or what I'm asking for, strip them down to an appropriate length if necessary, and recycle them. [Update: by exam problems, I mean the actual exam, not the sample problems.]

Some HW/exam problems are too long for the exam. Those problems will be shortened (perhaps only asking part a out of several parts). Some HW/exam problems involve too much time-consuming math for an exam, those problems will be modified to be less tedious.

So, there you go: all you need to do is understand how the old problems are worked (they will not be used verbatim, so copying them is of limited utility), and you are all set.

Again, you can bring in 2 formula sheets - either 2 sheets front & back, or 4 sheets with one side only. I'll provide all the basic formulas you need.

And, as a reminder, the final is this Friday at 8am in the usual room.

Thursday, December 2, 2010

Slides for 2 Dec 2010 lecture

UPDATE: the revised slides I actually used are at the same link below. Not many changes.

Here is an outline of tomorrow's lecture. My first draft of the slides are here, 15Mb PDF. Given that it is the second-to-last day of classes, I suppose you can check these out and decide whether to come or not ;-) For you EE-types, a lot of this stuff (like the truth tables and logic gates) is either the familiar subject of your recurring nightmares, or it will be soon.

The outline, as of now:
  • basic computer architecture
  • memory 
    • reminder: how transistors work
    • FLASH memory
    • S/D/MRAM basics 
    • memory architecture
  • logic & computation
    • how to implement logic & computation
    • logic gates 
    • building gates from transistors/switches
    • computation example: comparison, addition
  • information physics
    • energy requirements & thermal stability
    • mechanical, electrical, and magnetic storage
    • losses per cycle
    • the safety of Moore's "law" and fundamental limits
  • Time permitting (probably not): hard disks
    • overview of operation
    • media (analogous to CD/vinyl)
    • reading & writing
    • positioning & mechanical
    • why magnets?
    • history & recent boom times
    • fundamental limits approaching
 No, this is not on the final.

Tuesday, November 30, 2010

PH253 last lecture: computer logic & memories

It seems flash/ram/etc has won the day, so my last lecture of the semester will be on computer architecture, logic, and memory from a physics-y point of view. Invite your friends ;-)

The rough plan will be this:
  • What is our current high-level computer architecture?
  • How does one make memory/logic? What components are required? How do they work?
  • How do we currently build logic and memory?
  • How do (s/d)-ram and flash memories work?
  • What are the future prospects/promising new technologies?
  • Is Moore's "law" really in trouble? (Spoiler: it is not a law, and not yet.)
I think this will make a nice consistent logical flow, and all these topics are accessible with the physics we've covered. Time permitting, I would add:
  • A brief overview of how hard disks work
  • A brief overview of how mram might work (spoiler: it isn't ready yet)
  • Energy requirements/limitations for computation
This last lecture will be mostly 'show & tell' via powerpoint - almost no equations, mostly descriptive, but we've covered all the physics you need to understand these things. None of it will be on the final exam (neither will the material on LASERs from today).

Tuesday's lecture, evaluations

Today, in about 10 hours, we will figure out how lasers work. That's our last regular lecture, Thursday's lecture is still up to you, to an extent.

If you don't like lasers, here's another reason to attend: we'll do the department's discursive 'free-form' course evaluations at the end of the lecture. A good chance to give some (totally anonymous) feedback on what you'd like to see done differently, or not. I really do read all the evaluations and adapt based on the feedback.

The discursive evaluation is in addition to the online evaluation form for course evaluation you should have received email about already (probably a couple of times). Currently, only 26% of you have done the online evaluations, so please, please check your email (search for SOI if you have a lot of email) and fill out the college-wide evaluation. It takes 10 min at most, it is completely anonymous, and like the discursive evaluation, I take them very seriously when planning my courses.

PH253: Final Exam

Note that our final exam is Friday, 10 December from 8-10:30am. If you have already booked travel home before Friday, 10 December ... well, we have a problem, and we should talk.

Basic rules:
  • 12 problems, you choose 6 to solve.
  • If you do more than 6, I'll grade the best 6.
  • Comprehensive - basically everything through last week will be on the exam (i.e., nothing on this week's lectures).
  • Formula sheets will be given - they will be an agglomeration of the formula sheets from the first two exams, plus whatever is necessary from the material after exam 2.
  • You can bring 2 of your own sheets of 8.5x11 paper, double sided (or 4 sheets single sided).
Topics, roughly
  • Relativity
  • Radiation (accelerated charges, blackbody)
  • Photoelectric/Compton/photons
  • Wave-particle; de Broglie
  • Schrodinger's equation, 1D potentials
  • Bohr atom
  • Hydrogen in 3D
  • Angular momentum & spin
  • molecules & bonding
  • Multi-electron atoms & the periodic table
  • periodic solids, energy bands, metals-insulators-semiconductors
  • particle statistics
Definitely not on the final, but covered in class:
  • LASERs
  • variational method
  • p-n junctions (diodes), transistors
  • whatever we do for the last lecture
Gaming the system:
  • I listed12 topics. There are 12 problems. You have to solve 6 of them. Logically, you are responsible for only half the material. Pick your half carefully - if there are 1 or 2 topics you are sure you will not 'get' in time, skip them.
  • I will reuse old HW and exam questions, from this semester and last semester. Most questions will be new, but there will be a few recycled ones.
  • Letting you bring your own sheets is often a trap. If I let you bring all that in, how much could it really help you? You might get lucky printing out old exam/HW questions, but the odds are not great.
  • Work old HW/exam problems. The exam is about solving problems, so you should do that to prepare. I'm also likely to ask the same sorts of problems I have before, if not the same thing exactly.
  • Ask questions during the exam! I will often give out a startling amount of information if you're brave enough to ask during the exam.
  • Sleep. You will need your wits about you - the final will be more about cleverness than regurgitation, so cramming the night before will will probably hurt more than it helps. That being said, arrive properly caffeinated. I will. I will probably also bring a thoroughly unhealthy breakfast snack for you.

PH253: one more extra-credit possibility

One last chance for extra credit, the procedure is much like the last time. Due at the start of the Final exam.
  1. You watch one of these lectures (about an hour each). They are very good, and aimed at a lay-audience (you are well above that, having had at least 3 physics courses so far**), and Feynman is generally very entertaining.***
  2. You write me 3 page (8.5x11 in paper, 1.5 inch margins, 12pt font, single spaced) paper covering
  • Two new things you learned from the lecture (or things you understood better)
  • One way the lecture tied in to PH253
  • One way the lecture tied in to your major/field of study
  • One way the lecture tied in to everyday life
Do this, and I give you as much as +2% on your overall grade at the end of the semester, depending on quality of your writeup.* This extra credit opportunity requires a bit more writing (3 times as much, I guess), but on the other hand, the other one required you to actually attend something. I figure it about even.

To give you an idea of what 2% means:
  • There will be about 10 HW sets. Each is worth about 1% of your grade. This is 2 free HW sets. Typing up a three pages should and watching a video should take a minuscule amount of time compared to two of my HW sets :-)
  • Each hour exam is 30% of your grade, each question on the exam about 6%. This is like adding 3 points to your lowest exam question.
*If you are a non-native English speaker, this will be taken into account. English grammar and spelling is very silly.
**More like 'at least 2.7', since 30% of your PH253 grade is still to come ...
***Also, thanks to Bill Gates for making these lectures available ...

PH253: more grades on Moodle

Just uploaded HW8 grades, which leaves only HW9 outstanding at the moment. I'll try to have that by the end of the week.

Tuesday, November 23, 2010

PH253: last lecture

We have two lectures left. One is Nov 30, when we'll finish our discussion of particle statistics and figure out how lasers work. The second is Dec 3, our last class meeting.

I have not decided what I would prefer to do on Dec 3 myself yet, but as promised I'm open to any (reasonable and physics-related) suggestions for topics. Anything at least tangentially-related to the material we've covered I'm willing to give a lecture on. You can email your suggestions, or leave comments here, but just about anything goes. I will indicate if I think the topic you suggest is inappropriate or too detailed to explain clearly in one class.

My own suggestions, in no particular order:
  • more on transistors & semiconductor electronics
  • information storage technologies (hard disks, ram, flash, etc.)
  • two-level systems & resonance
  • applications of particle statistics (chemical kinetics, diffusion, etc)
  • crystals, geometry, & diffraction
  • magnetic materials
Don't feel confined by this list of topics, they are just a few things I would have liked to have covered if there were more time.

PH253: notes from today

Today's lecture was mostly drawn from the Feynman lectures, vol III, ch. 3-4. My own notes from last semester are here. (I didn't change much this time around.)

Monday, November 22, 2010

Student opinions of instruction

Reminder, you should be doing your course evaluations (student opinions of instruction, or SOI) right about now.

College-wide course evaluations are completely online. You should have received email instructions by now, and have until 5 Dec to complete your course evaluation. We take these very seriously, they are anonymous, and we cannot see even the aggregate results until well after your grades have been posted (at no point, ever, can we see who posted what comment, it remains totally anonymous).

PH253: last homework set

Here you go. Last HW set, due on the last day of class. For those of you attending the last few classes, we will go over the tougher problems.

Keep in mind I drop one homework set, so if you've done them all so far ...

Monday, November 15, 2010

PH253: Moodle grade update

Moodle is up to date through HW7 now (as well as including late HW and exam 2 alterations).

Wednesday, November 10, 2010

PH253: what is the point of HW9?

This week's homework is difficult, I grant you that, but not without reason.

*The first two problems are really our first stab at calculating the properties of real, everyday, useful materials (not that H is not useful or interesting, I guess). The vibrational frequency you'll calculate for KCl matches experiments amazingly well, in spite of the simple model potential used.

* The variational principle is something you will come across again, probably in mechanics (PH301/2) if not quantum. It is more or less a powerful way to come up with a best guess solution to a problem without actually solving it, and therefore powerful. There exist even more powerful methods commonly used in Chemistry and Physics for calculating the electronic properties of materials (e.g., Hartree-Fock, Density Functional Theory), but they are far more difficult. Should you encounter them, you're likely to be thrown in the deep end; the point of problems 3&4 is to give you a taste of how to handle systems which cannot be treated exactly without all the mathematical baggage that can obscure the essential simplicity of the method.

* Coupled oscillators can be used to explain a really ridiculous number of phenomena. In Thursday's lecture, we'll used a coupled oscillator model to (more simply) re-derive all of what we've learned of bonding, and cast it in a form that looks suspiciously like masses & springs or coupled LC oscillators. With this new approach, we'll be able to extend our analysis to the case of periodic solids (like semiconductor crystals, leading us to transistors and such). We'll be able to explain why some stuff is electrically conducting and other stuff is not, and why real materials behave the way you do. Problem 5 is meant to get you thinking about how coupled oscillators work as a preface to that lecture. It also gives you some hints on how one can spectroscopically identify different molecules (look for radiation emission/absorption matching the vibrational frequencies) or when molecules are adsorbed on a surface, e.g., in catalysis (new vibrational modes show up compared to the original molecule).

So, in short (if it isn't too late for that), think of this problem set as a preview of what's to come - both how we'll figure out how to calculate the properties of real materials, and what you're going to be up against in later courses. Most of what we've done the last month or two has been leading up to this.

Tuesday, November 9, 2010

Supplemental notes on chemical bonding

The variational principle and chemical bonding. These are some scanned notes from when I was an undergrad, related to last Thursday's and today's lectures.

Monday, November 8, 2010

PH253: Exam 2

Exam 2 grades are now on Moodle. You'll get them back tomorrow.

Friday, November 5, 2010

PH253: HW9

UPDATE: small change to 5c: you can assume the masses and springs are equivalent.

HW9 is out, due next Friday 12 Nov. There are only 5 questions, but you will not like them. ;-)

There will be plenty of hints in the coming week. You will need to recall a bit of mechanics.

Thursday, November 4, 2010

PH253: grades

Moodle grades are now updated through HW5. Your overall average drops the lowest HW set.

Later today I should have it updated through HW6 at least, and over the weekend Exam 2 will be there.

Tuesday, November 2, 2010

PH253: notes from the last week or so

Here are some scanned notes (from last semester) on what was covered while I was away. The parts where I refer to homework are from last semester's homework 8. These are more or less the notes I gave Dr. Mankey to use; any errors are mine.

If you think your electronics labs are too tough

These guys had it worse. Constructing a radio receiver from what could be scrounged from a POW camp. Including building their own resistors, capacitors, and rectifiers. Pretty crazy.

Monday, November 1, 2010

HW7 solutions / HW8 due date

HW7 solutions are out. This time, we heavily abuse Wolfram Alpha to avoid a great deal of tedium.

HW8 is due tomorrow, Nov 2. I did not note the time that it was due, but it is the usual 11:59pm ... so you have about 25 hours to go yet.

Good thing, since apparently many of you are affected by a power outage at the moment ...

PH253: Exam 2

Exam 2 is this Thursday, Nov. 4 during the normal class period. The rules are basically the same as last time:
  • You can bring in one sheet of normal 8.5x11in paper front & back, or two sheets using one side only on each. 
  • You will also get a formula sheet with the exam.
  • There will be 6 problems, you choose 4 to solve.
The coverage for the exam is, referring to your textbook sections:
  • 2.4.4-8, 2.5 Wave functions, Schrodinger, etc.
  • 3.2.1 Bohr model
  • 3.3 Hydrogen
The relevant homework sets from this semester are HW4-7; additionally HW4-7 from this past spring are relevant (as is exam II and the final exam from this past spring).

I will draw all of the problems problems directly from your homework from this semester and the homework from last semester listed above (though in somewhat abbreviated form).

Study those sections of the text and your notes, look at the HW sets mentioned, and you will be fine. It is extremely unlikely that practice problems will appear.

I will try to post the formula sheet tomorrow (Wed) so you know what you don't need to bother including on your own sheet.

PH253: HW8 #2

Check it. Good idea to google the phrases I put in italics.

Wednesday, October 20, 2010

PH253: HW8 is out

Here you go, due Nov 2. I'll be back in town on Oct. 31 and reading email for last-minute questions, and around on Mon Nov 1 all day.

Saturday, October 9, 2010

Make your own spectrometer / misc

This is awesome. Cell phone spectrometer ...

In other news: I've been unavoidably detained by advising issues the last day or so, but I will be updating Moodle grades, putting out HW6 solutions, and posting HW7 over the weekend. HW7 will not be due until ~Friday next week since I'm delayed in posting it.

Tuesday, we will look at the angular parts of the hydrogen atom solution we ignored so far, and figure out what p, d, and f orbitals are all about. That will run in to Thursday, but by the end of the week we'll have a good understanding of atomic orbitals, ideally.

Tuesday, October 5, 2010

PH253: Public talk

Dr. Orzel has been nice enough to post his slides, so if you were not able to make the lecture, you can complete the extra credit assignment by reading his slides and sample book material. Write a page on what you learned.

PH253: Physics help desk

Good news everyone, I've negotiated with the PH10x TAs, and they have agreed that it is OK if you come by the physics help desk for PH253 homework questions.* You can find the help desk hours here. The following TAs explicitly agreed to help with PH253 questions:

Lei Lu, Zachary Burell, Arindam Das, Jason Carson, Chockalingam Sivakumar, Sahar Keshavarz, Christopher Sterpka, Andrea Chaney

I didn't hear back from a few of the TAs when I asked if it was OK for you to come by, but the list above covers most of the available help desk hours. (I said that a lack of response would be construed as a 'yes' on their part though.) I agreed to send them the HW solutions in advance each week so they can better help you.

*Previously, the help desk was only for 100-level physics, but I asked if they would expand their repertoire.

Friday, October 1, 2010

PH253: Unsavory HW6 typo

Indeed, you are right: in problem 1 the width of the well is 2a, not a as I listed originally. The well extends from x=-a to x=a, and has V=0 over that interval. For |x|>a, the potential is infinite. That is why the normalization constant is 1/sqrt(a), not sqrt(2/a).

I've corrected that on the problem set, available at the same place.

Physics tutoring

Two options:

1) I am going to negotiate with the grad students running the physics help desk to let you go to their hours for help. They are only expected to help out with 100-level physics at the moment, but I think they'd be happy to help. Presume you can go to their office hours listed in the link above unless I tell you otherwise ...

2) The physics student society runs study sessions every Sunday evening at 6pm in 109 Gallalee. It is not organized per se, but a group of physics students that get together to work on homework collectively. A lot of them are upper-level students who have already been through PH253, so they can help. I've talked to them, and they are happy to work with anyone who shows up. The main entrance is locked on Sunday, but usually they will have someone manning the quad-side door periodically to let people in. This might be the even better option, sometimes getting some help from someone who was in your position not so long ago is the best.

Thursday, September 30, 2010

Public talk this evening

We had a good turn out, I saw quite a few of you there. I though it was a great talk, particularly relevant to what we've been covering lately (down to the fact that he used some of the same images/videos I've posted here). I really liked the football throwing explanation of particle tunneling ... it is important to know your audience.* Thanks for making a good showing for Dr. Orzel!

If you couldn't make either of his lectures today, you can still do the extra credit assignment. The first chapter of his book (and a dramatic reading of chapter 3) are available here. Chapter 1 discusses the wave particle duality (which we spent quite a bit of time on). In lieu of attending the talk, you can read it and write me a page about what you learned from it according to the previous rules. It is a good read, and I highly recommend the whole book. (And no, I don't get anything for saying that, I met Dr. Orzel for the first time today.)

*That's not to say that my brown bottle explanation of tunneling this morning was making a comment about what you do in your spare time, but it seemed like an everyday thing you could all at least imagine, even if lacking the requisite first-hand experience. I clearly need more football-based explanations.

PH253: HW6 is out

Due next Wednesday ...

Also, a nice applet for visualizing wave functions.

Wednesday, September 29, 2010

PH253: Wave functions

Hyperphysics is good stuff. Good example calculations/solutions and explanations of Schrodinger's equation.

Everyday life is basically understood

Interesting couple of posts.


The basic argument is that while everyday phenomena can be hideously complex (turbulence, for example), the basic laws governing them are completely understood. There is no everyday example of something that violates quantum mechanics or relativity, you have to go well beyond the everyday to find situations where we don't even know the basic rules that apply.

Of course, knowing the basic laws (i.e., equations) is one thing. Solving them is completely another, plenty to keep scientists gainfully employed for some time to come.

PH253: Exam 1 scaling

Long story short, it didn't really work out to simply add points to everyone's score or take the best 4 of 5. I suppose this is a common theme if you read the news, but either of those benefited the grade-rich quite nicely, but did little for those of you who really needed a boost. Luckily, our problem has a nice solution.

PH253: online grades

I now finally have the system set up so you can log in and see your grades (HW1-3 and Exam 1 right now). Since I am still young enough to be idealistic, I'm using an open source system called Moodle. Apparently you still have to pay if you want a sensible name. Instructions below the jump ...

PH253: Extra credit possibility

I posted last week that we'll have a special physics lecture Thursday evening. I think it will be really fun, and directly relevant to our course material. So here's the deal
  1. You attend the lecture.
  2. You write me 1 page (8.5x11 in paper, 1.5 inch margins, 12pt font, single spaced) covering
  • One new thing you learned from the lecture
  • One way the lecture tied in to PH253
  • One way the lecture tied in to your major/field of study
  • One way the lecture tied in to everyday life
Do this, and I give you as much as +2% on your overall grade at the end of the semester, depending on quality of your writeup.*

To give you an idea of what 2% means:

  • There will be about 10 HW sets. Each is worth about 1% of your grade. This is 2 free HW sets. Typing up a single page should take a minuscule amount of time compared to my HW sets :-)
  • Each exam is 30% of your grade, each question on the exam about 6%. This is like adding 3 points to your lowest exam question.

The speaker has a very good blog here, and a highly entertaining and interesting book you might check out.

*If you are a non-native English speaker, this will be taken into account. English grammar and spelling is very silly.

Tuesday, September 28, 2010

Some random plots related to the exam: average score by question, percentage of you choosing that question, and grade distributions for raw scores (5 questions) and with the proposed scaling (best 4 out of 5). Click on the picture for a larger version.

More details to come as I think about this a bit more ...

PH253: Exam 1 solution

Here you go. UPDATE: typo in #1 fixed - I missed a couple of primes.

Friday, September 24, 2010

PH253: HW5, misc

Here is the exam you took yesterday. Your HW5 is to solve the two problems you didn't choose on the exam, due Monday before midnight. My suspicion is that a few of you get together in a group, you've probably solved them all amongst you ...

Also, I'll have your exams back on Tuesday at the start of class.

A recent tour-de-force experiment by NIST managed to demonstrate gravitational time dilation on ordinary length scales. Neat stuff. (We didn't really cover gravitational time dilation, part of general relativity, but there is a small bit on it in your textbook.)

Wednesday, September 22, 2010

PH253: exam formula sheet


PH253: random exam hints

Just sent this as an email to one of you:

I think the best thing to study right now would be 1) the practice problems I put out - I will use one or two of them directly on the exam, and 2) this semester's and last semester's homework problems, focusing on the shorter problems (not the really lengthy and mathematical ones). The exam questions will be easier than most HW problems, but covering similar topics.
The book doesn't have many good problems for 2.4.1-2, I have to admit. The problems on uncertainty will be like numbers 9 & 10 on the practice problems - using a de Broglie wavelength and the uncertainty principle together, but in a more or less straightforward way. If you can do those two problems, you are more or less OK on 2.4.1-2.
For Compton scattering, just read the notes I put out, and that should be enough.
For relativity, the sample problems are good.
For the Photoelectric effect, there is really only the one equation - it will have to be something like given wavelengths and voltages, find the work function ... not much else to ask.
For photons & the quantum hypothesis, questions will be like something like the HW problem finding the number of photons per second put out by a radio transmitter.

For radiation, it will be a simple example like given an acceleration, find the power radiated by a charge, or the energy radiated in a time t (E = Pt).

Today's schedule, approximately

I have meetings from about 1-3, so today is a bit less open than I had hoped. Here is when (and where) I'm likely to be available:

11-12:30 Gallalee 110
~3-5:30 Bevill 2012

I'll be reading email regularly this evening for last minute questions as well. I will try to be in Gallalee by about 10:00 tomorrow for any truly last-minute questions.

Tuesday, September 21, 2010

Special colloquium next week!

Next week, on Thursday, 30 September at 7:30pm, we are having a very interesting public talk in 227 Gallalee:

"What Every Dog Should Know About Quantum Physics" by Dr. Chad Orzel of Union College

Chad Orzel is the author of a popular physics blog called Uncertain Principles: http://scienceblogs.com/principles/

and the author of a book titled "How to Teach Physics to Your Dog"

Chad Orzel's bio can be found here:

Here is an abstract for Chad's public talk:

Quantum physics, the science of extremely small things like atoms and subatomic particles, is one of the best tested theories in the history of science, and also one of the most bizarre. Many of its predictions -- particles that behave like waves, cats that are alive and dead at the same time, objects that pass through barriers as if they weren't even there -- seem more like science fiction than science fact. This talk will explain the reality behind some of the stranger aspects of quantum physics, and why it is so important that even dogs should know about it.

Monday, September 20, 2010

PH253: Exam 1 practice problems

Here you are. It is unlikely that there will detailed solutions before Thursday, but I will try.

Remember, the exam has 7 problems and you must do 5 of them. I will provide a formula sheet with all the necessary equations & constants (an example of which will show up tonight or tomorrow), what you put on the sheet you're allowed to bring in is up to you.

It will be important that you manage your time -- don't get stuck on any one problem too long, since you have the freedom to skip two of them. If you really don't know how to go about a problem, don't freak out: just pick another one. Choose your problems carefully, and start with the ones you think are easiest.

PH253: Exam 1 coverage

Reminder: Exam 1 is this Thursday during the normal class period.

Sections of the textbook covered on Exam I:

  • 1.2.1, 1.2.2 EM Waves
  • 1.3 Special relativity 
  • 1.5.1-3 Appendix to special relativity
  • 2.1.1-3, 2.1.5-6 Quantum hypothesis & radiation
  • 2.2.1-3 Photoelectric
  • 2.3.1-3 Photons / Compton
  • 2.4.1, 2.4.2 de Broglie, uncertainty

Things not in the textbook on Exam I (from notes provided):

  • Power radiated by an accelerated charge (no derivations, just the Larmor formula)
  • More detailed discussion of Compton scattering

Remember that you can bring in one standard 8.5x11in sheet of paper with formulas, etc., front & back. If you write on only one side, you can bring 2 sheets. Bring a calculator.

A few more practice problems will show up this evening.

PH255: Writing a scientific paper

Lab reports are a real pain, and I know many of you in PH255 have been struggling with how to go about writing a lab report. Here's how I usually go about writing a paper:

PH253: HW4 solutions

Here you are.

Wednesday, September 15, 2010

PH253: HW4 hints

I'll be updating these through the evening as I finish them up. The link will be persistent. I'll post here when they are complete.

UPDATE: barring any typos I find later, the hints are about as complete as they are going to get.

PH253: HW4 typo

Fixed a typo on number 2; both uncertainty relationships should be > h/4pi, not > 4pi. Same link as before.

Sunday, September 12, 2010

PH253: HW4 is out

Here you are. As usual, we will do a number of them in class. A couple of quick notes in advance of more substantial hints:

  • For number 3, you will need to look up the intensity pattern for single-slit diffraction. Presume the electron must be confined within the central, most intense region, which gives you an estimate of position uncertainty.
  • I've asked number 6 before.
  • Number 7 is a famous thought experiment, it can be found in the wikipedia article on the uncertainty principle.
  • Number 8 is a straight math problem (math we'll need soon). Don't let the the unfamiliar terms stump you, all you need to do is integration and algebra for parts a-c.
UPDATE: fixed a few typos, in particular on number 8.

    Friday, September 10, 2010

    PH253: Textbook

    I loaned my textbook to someone until theirs came in. If your copy has come in, it would be nice to have my book back soon ... a colleague is asking to borrow it.

    Thursday, September 9, 2010

    Double slit applet

    A nice applet to illustrate the crazy double slit stuff we talked about today.  You can use photons, electrons, neutrons, and helium atoms, and even use multiple sources or vary the incident wavelength. Note the different modes - high intensity, single particles, and lasers. If you like, add a detector on one or both of the slits and watch the interference go away ... neat stuff.

    Also, the actual experiment with single electrons!

    How to read science papers without reading every word

    Nice read. Applies equally well to sections of a textbook, I think.

    PH253: Compton scattering notes

    Here are some notes on Compton scattering. And by 'notes' I really mean deriving the Compton equation, the photon and electron energies, etc., and not so much on the discursive side. They have not been heavily proofread yet, but I believe everything is substantially correct.

    Consider this your mathematical guide for Compton scattering (chock full of goodies related to the homework), with your textbook filling in the basic background.

    I would like to be able to keep up with notes on the same level as the blackbody notes for every topic, but it is unrealistic to do on the fly ... I'll provide what I can.

    Wednesday, September 8, 2010

    PH253: HW3 hints

    I'm starting a file of HW3 hints. Right now, there are hints for the first three problems, I will be updating it tonight and tomorrow to add more. Probably by class time tomorrow it will be as complete as it's going to get ... the URL will not change as I update the file. If you like, check here to look at the time stamp and see if it has been updated since you lacked looked.

    UPDATE: the hints are probably about as complete as they are going to get. A little something for each of the 9 problems.

    PH253: partial HW2 solutions

    I've got solutions to problems 1-5. Hope to have problems 6 & 7 finished tomorrow. Let me know if you find any typos or places that need clarification.

    UPDATE: there is a solution for problem 6 now. Only problem 7 remains, I will try to get a solution out Wed.

    Tuesday, September 7, 2010

    PH253: HW3 is out

    Shorter than the last two, I think. I asked a couple of these on HW last year, and we will cover a few of them almost directly in lecture.

    We should cover the bulk of the material on Compton scattering and the photoelectric effect on Tuesday, on Thursday we'll go over any remaining questions you might have.

    Thursday, September 2, 2010

    PH253: homework deadline extended

    You can turn in HW2 any time up until this coming Tuesday's class, 11am on 7 Sept 2010. I'll be posting more hints over the weekend, and will be around Bevill this afternoon and tomorrow afternoon.

    (Also, some typos in the notes came up today, I'll fix them this afternoon/evening and post when it is done.)

    Wednesday, September 1, 2010

    PH253: HW 2.1

    For problem 1 on HW2,  you'll find this interesting. (Note the 'dot' notation to signify derivatives with respect to time.)

    PH253: key points from the last lecture

    The last lecture covered a lot of ground, but in the end there are really only two main things to take away from the last lecture:

    1) Accelerating charges radiate electromagnetic energy (a.k.a., light). The total radiated power P in terms of the acceleration a for a charge q is
    P = \frac{q^2a^2}{6\pi\epsilon_o c^3}
    This is only valid for velocities small compared to c - even though we correctly transformed the field according to relativity, we used the classical expression for acceleration. This expression is known as the Larmor formula.

    2) Since accelerating charges are radiating and therefore losing energy, they also experience a 'radiation reaction' force or a recoil due to the emission of radiation. This force is analogous to viscous drag or friction, and is given by
    F = \frac{q^2}{6\pi\epsilon_o c^3}\frac{d^3x}{dt^3} = \frac{q^2}{6\pi\epsilon_o c^3}\frac{da}{dt}
    Again, this is valid for low speeds compared to c, and is typically called the Abraham-Lorentz force. This force is unusual in many respects - for one, it represents the charge effectively acting on itself, and it depends on the rate of change of acceleration or the third derivative of position.

    Tuesday, August 31, 2010

    PH253 facebook group

    Find each other and commiserate. ;-)

    Supplemental texts

    In case you're wanting to review your E&M or mechanics ...
    • Serway & Jewett, "Physics for Scientists & Engineers" Vol 2 (the PH105/106 book). Covers mechanics and E&M
    • The Feynman Lectures on Physics (in the library or the physics student lounge on 1st floor). Three volumes, covers mechanics, E&M, and modern physics. I draw on these heavily in preparing lectures.
    • E.M. Purcell "Electricity and Magnetism" (should be in library; uses different units!). E&M only, but it has fantastic treatments of moving charges and radiation. The only downside is the use of cgs units, which are almost certainly unfamiliar to you, and which make the formulas look a little different.
    Feynman & Purcell are more mathematically sophisticated than Serway, both very casually use of vector calculus. For the most part, though, you should be able to follow the essential points even if you haven't seen some bits of the math.

    PH253: applet for tomorrow's lecture


    Lets you visualize the field from moving & accelerating charges. Drag the velocity slider to start & stop a charge in an inertial frame (what we'll start with) or set it in simple harmonic motion (SHO, what we'll end with).

    Monday, August 30, 2010

    Society of Physics Students (SPS) meeting this wed

    Passing on a note from the physics student society ... it isn't just for physics majors, but anyone interested in physics.
    The Society of Physics Students will be meeting in the SPS room (109 Gallalee) Wednesday at 5:30 PM. Pizza and drinks will be provided.

    The plan is for this first meeting to be a 'meet and greet' of sorts,  to let those that haven't been involved with SPS in the past learn what  it is we do, the benefits of joining the national organization, and how to do so.

    Immediately following this we'll have time to study and work on homework together, so if there's a physics problem that's had you stumped for a while, bring it in and chances are someone will have figured it out before and we can help you.

    Hope to see you there,

    Heath Gurganus
    President, UA Society of Physics Students

    PH253: homework 2 hints

    Check it. As will be our habit, we'll fully work some of the problems in class, and at least set up the rest. This homework is mathematically challenging in a few places, but I'll try to spend a little extra time on the most difficult spots

    (Also, notice that in the notes on radiation I've included some example problems toward the end ...)

    Tomorrow, we'll deal with accelerating charges and figure out where radiation comes from. In the notes I've written up, we'll start with 1.2.2 (Charges that start and stop) and try to get as far as the equation of motion for oscillating charges (1.3.5). Thursday, we'll continue from where we left off and finish off the rest.

    Again, I will probably skip some of the details in the notes to focus on the most important results. I tried to be as thorough as possible in the notes so you could see how everything we need can be derived from what we already saw in PH105 and PH106.

    Sunday, August 29, 2010

    PH253: HW1 solutions

    are out now. I solved several of them using the template to give you an idea of what I intend by the template. Let me know if you find any mistakes or need clarification on something.

    Saturday, August 28, 2010

    PH253: a word on homework

    So maybe you didn't quite finish homework 1. That's OK, turn in what you've got and it is better than a zero. So long as you're following the material, you will be fine. Keep in mind homework in total is only worth 10% of your grade, and I drop one problem set. There will be about 10 problem sets in total, so missing one whole set makes each of the others worth (1/9)*10%~1.1% of your grade. Missing (say) 2 problems out of 10 is only 20% of 1.1%, which is practically nothing.

    In other words, no big deal to miss a homework set or parts of one here and there if you've got other things pressing or just don't get a few problems. The main thing is to understand the material and work the problems out/read the solutions when you get some time, because similar things will show up on the exams ... which are worth quite a bit more. HW is mainly for practice and learning, the numerical consequences for your grade are minor.

    Thursday, August 26, 2010

    PH253: what is the speed of gravity?

    Related to the material for the next couple of lectures, in a way.

    PH253: slides for the next few lectures

    For the next ~3 lectures, here are some slides I might use related to the fields of charges in motion and radiation from accelerated charges.

    I say 'might' because I might decide to just draw on the board instead of messing with the projector. In any case, the PDF contains useful figures to go along with the lectures.

    PH253: HW1, redux; notes on radiation

    First, I've heavily updated the notes on radiation, the current version has the same URL. We'll start off by considering the E and B fields for observers in motion relative to the source, and work our way up to accelerating charges and radiation. Again, not all the sections in the notes will be covered (those with a * are considered optional), I was just trying to be thorough.*

    Second, I realized I forgot to give any hints on HW1 problems 5b,c and 10. I'll leave some time tomorrow for going over 5b,c and other questions you have, and 10 we will do in the course of the lecture. Note that for 5b velocity is the integral of acceleration through time. Set that up and realize it is separable (manipulate the du and dt's like fractions), and Wolfram knows the integral. For 5c, integrate once more, position is the integral of velocity through time. Problem 10 we're going to do in class as part of Thursday's lecture.

    * The main idea is: relativity -> field of a charge in motion -> charges that start or stop -> accelerating charges -> radiated power. Then, power -> radiation reaction force -> harmonic oscillating charge with damping and driving field -> radiation power of a charge exposed to a driving field. Last, relate radiated power to the energy density of the thermally-generated field oscillating charges bathe at temperature T in to get Rayleigh-Jeans, and add Planck's hypotheses to fix it. It will all make sense in time ...

    Wednesday, August 25, 2010

    PH253: notes for the next few lectures

    Over the next three lectures, we'll be discussing radiation (light emission) in detail, and in particular the spectrum of light emitted from hot objects ("blackbody radiation"). What we'll find is that the classical description is severely lacking, and this will lead us to the necessary development of quantum physics.

    I find the textbook derivations of blackbody radiation mostly obtuse, too rooted in esoteric historical baggage, and unnecessarily difficult. All this annoyed me enough to come up with some notes on radiation that will make up the bulk of the next three lectures. The notes are not quite complete yet (close, probably 'done' by Thursday), and there are a few extra bits included beyond what we'll probably cover in class.

    So, 1) don't be scared by the length of the notes, you're not responsible for all of it, 2) they are long because I purposely tried to only use PH105-106 material and relativity, 3) the gain in clarity will be worth the extra time in the end, and 4) I will spell out what material you are responsible for knowing on the exam, and it will mostly be what is in the textbook. The extra derivations are mostly just for clarity, you'll be responsible for the end result.

    Anyway, here's the basic plan for the next few lectures.

    Tuesday, August 24, 2010

    Just neat.

    By the end of PH253, you should have a good idea of how this works. I hope.

    PH253: Lecture 2

    Tuesday's lecture will cover the following:
    • Lorentz transformations (relating position, velocity, and time in different frames)
    • Space-time diagrams
    • Momentum
    • Energy
    • Force
    Last year's scanned notes are here, by the way.

    What we'll cover this week is a combination of the PH102 notes linked in the last post and most of what I have in the scanned notes entitled "relativity_L3.pdf." That corresponds to sections 1.3 and 1.5 in your textbook for Tuesday, on Thursday we'll (probably) spend most of the time applying relativity to what we already know of E&M. You can read either the textbook or the notes I'm linking, whatever you find more enlightening ...

    PH253: HW1 hints

    Tuesday, we'll set up most of the homework problems, time permitting. Thursday, we'll set up the remaining problems. Until then, below the fold are some hints on how to get started. I would agree that this HW is conceptually difficult, and requires a good knowledge of calculus in some spots. Later HW sets will be less conceptually challenging, but the math will not let up, sadly.

    Also, keep in mind I may have asked some of the same problems last semester, if you dig around the HW directory ... you may also try ph102.blogspot.com. Questions I've asked before, somewhere, sometime, have a * next to them below.

    Lastly, the PH102 notes I posted previously will be enough to get you through Tuesday's and Thursday's lectures. Though some of the derivations are missing, the basic results are there. For Thursday's lecture, check out the beginning of the chapter called "Magnetism" for a derivation of B from E.

    Thursday, August 19, 2010

    Lecture notes for relativity

    We'll be starting out with relativity for the first 2-3 classes (Ch. 1 of your text), and you might find some notes I wrote [23Mb PDF] useful as a supplement. The first chapter of the notes covers relativity; the rest should be review, but might still be helpful. The notes are for PH102, but that class actually covers relativity in about the same way (albeit a little less 'mathy').

    Also the slides I'll use for Tuesday's first lecture are here.

    Wednesday, August 18, 2010

    Monday, August 16, 2010

    PH253: Course schedule

    Your course schedule, as a simple spreadsheet, or a Google calendar.

    Note before booking any travel arrangements that we have that extra-awesome 8am Friday Dec. 10 final exam slot.

    Sunday, August 15, 2010

    PH253 Fall 2010 Syllabus

    Find it here.

    Homework template

    This is the format I'd like you to use for homework problems. You don't have to print out the template exactly, you can just fill out a sheet of paper in the same fashion. The main point is that I'd like to ensure that you're solving problems in a logical, organized way, with clarity and precision. The idea is that at first this will help reinforce a general, systematic approach to problem solving that will serve you well when the material gets harder.

    Your homework be graded on the appearance (if applicable) and quality of these items:
    • Find/Given - what are you supposed to find, and what have you been given?
    • Sketch - try to visualize the problem.
    • Relevant equations - identify what basic equations might be of some help.
    • Symbolic solution - without using numbers, algebraically find the desired quantity in terms of given quantities.
    • Numeric solution - if given, plug in any numbers given. 
    • Double check - using dimensional analysis, order-of-magnitude estimation, for example, see if your answer makes sense. In some cases, you might just solve the problem by a completely different technique.
    I'll describe this in some detail in class, and will try to follow the template when I'm solving problems in class. The format isn't as restrictive as it might seem at first, a lot of students find that it actually helps them organize their thoughts and get started on a problem that seemed incomprehensible at first.

    Tuesday, August 10, 2010

    Welcome to PH253/255 Fall 2010

    This is where you will find all the information you need for PH253 and PH255 this semester.

    First things first, here are the textbooks you'll be needing for each course:

    PH253 textbook.
    PH255 textbook.

    In another day or two, I will have the syllabus and some other details posted ...

    If you prefer, you can follow all this on twitter (@pleclair). Whenever there is a new blog post here, it will generate a tweet on my account using the hash tags #ph253 and #ph255. The opposite is also true: if I send out a course update via twitter, you can see it in the little box at right. And, of course, various apps will let you incorporate either the twitter or blog feed into your news feed.

    Thursday, May 6, 2010

    PH253: Final grades

    I have graded the finals (twice, actually, to be sure) and put the results up on Moodle. Your letter grades are also up on myBama.

    Your final exam scores and overall average now show up there; I will post the letter grades on myBama shortly. There are still some days to make changes if you notice errors, and feel free to email me with any questions.

    Monday, May 3, 2010

    PH253: grade update

    HW9 & 10 grades are up on moodle now, as is the extra credit for the major field exam. For the major field exam, you get 2.5% times your listed score as extra credit added to your overall course grade. Your overall average includes this (as well as dropping the lowest homework). HW10 replaces your lowest non-dropped HW score, if it is sufficiently good.

    For the final, since many of you are about to ask for last-minute suggestions:

    I think at this point, just reading the exam & homework solutions is the best thing to do. Some of the final questions will be very, very similar to those on HW sets and the two exams. There won't be any surprises.

    There will also be 1 or 2 very much like the practice problems, if you haven't been over them yet.

    There won't really be anything on molecules, lasers, or periodic solids.

    Tuesday, April 27, 2010

    Reminder: online course evaluations

    You should have received instructions on how to do teacher-course evaluations (TCEs) online this semester. Please take some time to complete the evaluations -- we do take them seriously. Right now, response rates are 52% (PH253) and 40% (PH255) ...

    Extra-credit exam

    For PH253, the aforementioned extra credit exam will give you a maximum 2.5% added on to your grade, scaled by your performance on the exam. It will not be specific to HW or Exam grades, it will simply add to your overall average.

    PH255 final presentations

    This week, the modern physics lab students will present the results of one of their more involved (2-week-long) experiments. You are all invited to attend, the presentations will tentatively be held in room 322 Gallalee. Schedule below the fold ...

    Monday, April 26, 2010

    PH253: Example problems for the final.

    Find the first batch here.

    They are by and large a bit shorter than what the final questions will look like, but if you can handle these, you can handle the final.

    More to follow on the remainder of the material, hopefully tonight. Answers/solutions will not be posted immediately so you give them a try first ...

    Things covered on the final

    Sections from the text on the final exam:

    Major field test

    Just to clarify: anyone in a 200+ level course can take the exam for extra credit, you don't have to be a physics major or anything. We want to assess our teaching as a whole, not just how our own majors are turning out.

    If you are planning to take the test, please email me if you haven't already -- I need RSVPs for a head count, since we have to pay for the tests on a per-seat basis ...

    Some final exam details to follow in a bit.

    Friday, April 23, 2010

    Alkali metals

    Remember how I told you alkali metals were desperately reactive?

    Direct link, in case embedding fails ...

    Right around "let's try cesium" one knows things are about to get interesting.

    (h/t, and more fun with chemistry)

    Thursday, April 22, 2010

    PH253 & PH255: Extra credit exam

    The details of the major field text ***NEXT WEDNESDAY**** (details of the extra credit for PH253 and PH255 to follow).

    The Dept. of Physics & Astronomy would like all sophomore,
    junior & senior Physics majors to take the Physics Major Field
    Test (MFT) next week,

    ** Wednesday 28 April in room 203 Gallalee **

    You may _START_ the exam any time between

    **  1-2:30pm    **

    You are allowed 2 hours for the exam.

    PH253: Thursday's lecture

    Today, there are two things in store.

    1) First, a short recap of what's cool about lasers, since I went a bit long last time ... associated with that, we're going to measure a laser's wavelength and angular beam divergence in the classroom. Seriously. Don't sit in the back if you want to hide, we'll need the whole room ;-)

    2) After that, we'll return to electrons in a periodic crystal lattice and figure out how the crystal geometry alters things like conductivity. As it turns out, the problem will reduce to a combination of our two usual approximations: springs and free electrons. This will lead us nicely into more detailed semiconductor physics.

    Finally, if you have any suggestions for a special topic next week, now is the time to suggest ... I'll need the weekend to learn it myself & make up a lecture, depending on how crazy the winning submission is.

    Tuesday, April 20, 2010

    PH253: Last two lectures / evaluations

    Next week, my rough plan was to talk about magnetic resonance and its applications (e.g., MRI) for at least one lecture. However, I'm not wedded to any particular plan.

    What would you like to hear about for the last lecture or possibly two? Anything tangentially considered an application of what we've learned this semester is fair game. Leave your suggestions in the comments; based on the number of submissions and plausibility I'll pick a couple of topics for next week.

    Unrelated: you should receive an email about doing online teacher-course evaluations (TCEs); we will not do the scantron bubble sheet evaluations in class ... it is all going online now. Please follow the link and fill out your evaluations in the next week or so, we do value this feedback. In class on Thursday, we'll do a short discursive evaluation (i.e., you write whatever you want), so that is a good day to show up to class.

    PH253: Cool laser simulation / Reading

    Based on what we talked about today, you should be able to figure out how to make this simulation work ...

    Also, today's lectures were based mostly on material from the Feynman lectures:
    Volume III, Ch. 4 (Ch. 3 as a reminder)
    Volume I, Ch. 42 (Ch. 40, 41 as a reminder)

    I also made use of Solymar & Walsh (Ch. 12) for specific examples of laser systems. Again, note the (now 10 part) series on cool laser applications over here.

    PH253: Grades

    Moodle is now updated through HW8. Only thing missing right now is HW8 ...

    Amazing laser applications

    A (so-far) 9-part series of amazing laser applications.

    Coincidentally, we'll figure out how lasers work in Tuesday's lecture. We'll start from where we left of with particle statistics, and figure out the 'stimulated emission' part of the acronym first. Once we have the key bits in place, I'll talk briefly about how one goes about constructing a laser,  and why they are not just fancy flashlights.

    Well, they are fancy flashlights, but they do other things too ...

    Monday, April 19, 2010

    Extra-credit possibility

    For both PH253 and PH255, see the note from our department chair below. If you participate in the major field test, you will receive some sort of extra credit (tied to performance on the exam) for both PH253 and PH255. Details TBD.
    Our annual offering of the Major Field Test in Physics will
    be Tuesday afternoon of next week, 27 April ... more exact
    time and place still to be determined.

    This test helps us assess how well our undergraduate courses
    are doing for you.  It is not a test you need to study for, but
    it provides extra credit for those of you who are enrolled
    in 200-, 300-, and 400-level physics and astronomy courses.
    The amount of extra credit is tied to how well you do on the
    exam.  We also will provide snacks during the exam and
    there will be prizes for the top sophomore, junior and senior

    We are still trying to sort out logistics, but I wanted to give
    you a week's notice for the exam.

    More information will be coming soon.

    PH253 & PH255: Course evaluations

    This week is course evaluation week. Your chance to make up for any perceived injustices ;-)

    For PH253, evaluations will happen this Thursday. If you were not otherwise planning to attend class, this might be a good reason.

    For PH255, evaluations will happen *next* Monday.

    PH253: HW10

    This one is entirely for bonus points, more or less. It can't hurt your grade in any way.

    The exam will be posted soon, but for now you have your own copy that you picked up in class ... right?

    Thursday, April 15, 2010

    PH253: Exam 2 results

    First: the grades for exam 2, and your updated overall average, are on moodle now. You'll get the exams back in lecture ... about 8.5 hours from now.

    Second: it was not as bad as you had feared, but as a whole you did fall for the straightforward-but-mathematically-tedious traps (problems 2 & 6, mostly). The alternative was problems 4 & 5, which were very simple with little calculation if you remembered what to do.

    Third: here are some interesting plots.
    The distribution was far less weird this time -- about an equal number of A, B, and C grades, which is not bad at all. The average was 81.3%, with a standard deviation of 12.6% (N=46).

    A few little things I found interesting:
    • You did very well on #1, which means you really looked at the practice problems (it was the same).
    • Only #2 was strangely low; it was hard, but it was also a homework problem (HW5).
    • A surprising number of people chose number 6, despite it being the obvious trap on this exam. It was straightforward, but a serious time sink. Myself, I would have skipped it. I graded fairly generously on that one if you had algebraic issues but the method was basically ok.
    More details and solutions tomorrow ...

    Tuesday, April 13, 2010

    PH253: Last-minute cramming

    Anyone who told you last-minute studying is not helpful never tried it. (A good night's sleep is still good, when you can get it.)
    • Understand how to find the equilibrium spacing, given a potential U(r). Remember how to find the maximum force?
    • Understand how a set of spectral lines splits in a magnetic field (HW8 #2).
    • Choose your problems carefully! Some are traps, to be safely sprung only by the most mathematically adept ... (that is, some problems are very tedious unless you are a math savant).
    • You did quite a bit of work with hydrogen wave functions. Remember it.
    • HW5 #7: all physicists love the harmonic oscillator to a fault. You will see it in every PH course, this one included.

    Monday, April 12, 2010

    PH253: draft of formula sheet

    Here is a rough draft of the formula sheet. The final version will look basically like this one, possibly with a few small additions (I am very unlikely to finish this in time to post another version tonight though.)

    PH253: HW5, #2 error in solution

    On HW 5, problem 2, the correct answer should be 118.5nm for the wavelength, not 11.85 as I previously reported in the solutions. (The posted solutions are now fixed.)

    If you would, make sure that you were not deducted points for having the right answer ... if you were, please bring your HW5 to class on Tuesday or Thursday and I'll give back the deducted points.

    Thanks to Mr. Warren for pointing this out!

    Sunday, April 11, 2010

    PH253: HW solutions, Exam II

    UPDATE 6: Number 9 now also has a solution; multiple bugfixes.

    UPDATE 5: Minor bugfixes.

    UPDATE 4: Solved through problem 8.

    UPDATE 3: Solved through problem 6.

    UPDATE 2: Some tedious/difficult problems removed. The first 4 problems now have solutions.

    UPDATE: Quite a few more example problems added, and a full solution for the first two. Same link as below. More solutions should follow in the next hour or two.

    A few items in advance of exam II:
    • HW 8 and 9 have solutions.
    • A few sample problems, with answers. More will appear tonight; probably very, very late. It is unlikely full solutions will appear in time, but I'll see what I can do. I will at least try to add some hints.
    • An example formula sheet will be posted before the exam, but probably not until Monday afternoon or evening. It takes a long time to prepare. Longer than the exam, in fact.
    • I have not had any email contact since Friday evening ... I hope to catch up on most of my email this evening.

    Thursday, April 8, 2010

    PH253: Sucking a little bit less at grades

    Moodle is now up to date (ostensibly) through HW 6 & 7.  HW8 should be graded and back to you on Tuesday, if all goes well. Let me know if you see any errors, etc. There is a new column "Overall average (with drops)" that accounts for dropping your lowest homework grade. The extra credit for doing part 4b on exam 1 and the make-up exam are now factored in as well.*

    *If the make-up didn't help your exam grade, it got added to the overall homework effort. Part 4b of exam 1 added +1.5% to your exam score - no matter how high or low - for full credit.

    PH253: Material for Exam II

    Your next exam is this coming Tuesday. Here are the sections I consider fair game:

    Wednesday, April 7, 2010

    PH253: Notes

    All of my notes (I think) since the last exam are now online. Find them here. Each file contains (in general) several lectures worth of stuff, the filenames are a decent guide.

    Newly scanned:
    Matter waves, Schrodinger equation, 1-D potentials
    Hydrogen atom
    Angular momentum, spin, atomic spectra, helium
    Variational method for molecules, crystals & energy bands
    Identical particles & statistics
    A supplement on chemical bonding (a handout from an UG course I took eons ago).

    Some form of HW 8 & 9 solutions will come out tonight (probably handwritten ones for now), as well as guidelines for next week's exam and possible some sample questions.

    Tuesday, April 6, 2010

    PH253: HW 10 will not come until after the exam

    Uh, that was it. Start studying ;-)

    Details of what the exam will cover should show up tomorrow.

    (The exam is this coming Tuesday, by the way. See here.)

    Monday, April 5, 2010

    PH255: final labs schedule

    For the final 4 weeks, you'll be performing two different two-week-long experiments. These experiments are less guided than the single week experiments you have been doing so far; you'll be given a basic task and some background information, and it is up to you to figure out and complete the experiment (though not without help!).

    Here's the schedule:

    Wednesday, March 31, 2010

    PH253: HW9 deadline extended

    I feel like this homework set is coming due a bit too quickly, based on what we covered on Tuesday and what I want to do tomorrow. I'd rather you not rush it, and have some time to understand the problems.

    Therefore: the homework deadline is extended until Tuesday, 6 April at midnight. Spread the word ...

    PH253: molecular orbitals

    Here's a nice introduction to the variational method and the linear combination of atomic orbitals (LCAO) we were talking about last time. It describes some further approximations that one can use to do calculations on molecular systems, and the level is about the same as our last class (modulo a bit of linear algebra). Those of you in chemistry classes should be able to follow it pretty easily I guess.

    PH253: HW9 hints

    Copious hints on HW9 below the fold ...

    PH253: Thursday's plan

    Thursday, we'll go over the variational method for bonding again, and do a couple of examples to show you how the method really works. Today (Tuesday) we went over the general scheme for molecular orbitals, we'll expand on that to figure out how simple hydrocarbons and such things work.

    From this we'll find the pi and sigma orbitals you've probably heard so much about in Chemistry class, the basis for starting organic chemistry. From there, we'll be able to figure out some methods for handling a whole solid's worth of atoms and the electronics properties of metals, semiconductors, and insulators. With a few more details, next week we'll be calculating the properties of realistic materials.

    In other news, I'll be posting some heavy-duty homework hints on Wednesday to get you started, and we'll do a couple of problems in class on Thursday.

    Tuesday, March 30, 2010

    PH253: HW9 omission

    In problem number 5, I forgot to give you the dissociation energy ... Ed = 3.37eV. This is corrected in the version of the HW now online.

    Thursday, March 25, 2010

    PH253: HW is due friday

    You know the homework is due on Friday, right? Like it says on both the google calendar and the instructions box on the HW set itself ...

    Just wondering, since I seem to be getting a lot of early homework, and I can't stress enough how unusual that is. ;-)

    Scientists versus science fans

    There is truth in this. We invented the symbol so we don't have to bother memorizing digits ... just like you solve problem symbolically so you've solved all problems of that class, not just one particular example.

    Of course, there is only one digit of pi in base pi. The rest of the numbers are a real pain then, however.

    PH253: office hours the rest of the week

    Office hours are going to be tight today owing to a number of unsavory meetings. Best times are:

    11-12 in Gallalee
    12-2:30 in Bevill

    Friday is proving tough as well. Best times are:

    11-1 Bevill
    3:30-5 Gallalee

    I will be reading email continuously though (and catching up on Wednesday's email shortly I hope).

    Wednesday, March 24, 2010

    PH253: Schedule

    I've updated the Google calendar to reflect our adapted schedule ... have a look. Clicking on any class event and showing event details will tell you what sections of the book are relevant for that day.

    Basically, compared to the original schedule, we are doing more solid state physics + applications and skip the sections on nuclear/particle physics (as it will be covered in the new PH354 'Intermediate Modern Physics' curriculum from now on).

    If you'd rather just have a printed schedule, look here. Same information, but you can see it all at once ...

    Note that the very last lecture (29 Apr) is partly final exam review, and partly 'viewer's choice' ... that means I'm open to suggestions for what you want the final lecture to be about. Most anything plausibly PH (or CH or ECE or MTE) related is fair game ... give me some suggestions for a topic you think we miss during the semester, and I'll try to prepare a short lecture on it.

    Tuesday, March 23, 2010

    Double slit experiment

    Cool images/explanation and video of an electron double-slit experiment, courtesy Hitachi. Time-lapse of single-electron microscopy ... does not get much more direct than this. Spooky, but true.

    (Some companies still do really cool R&D. More nuggets to be mined on the Hitachi site ...)

    Monday, March 22, 2010

    Sunday, March 21, 2010

    PH253: HW8 is out

    Here it is. Due on Friday 26 Mar; we'll go over many of these in class. You can find the figures here, for a couple of the problems it might be easier to just draw on the figures.

    Saturday, March 13, 2010

    Spring Break

    Turning in homework at midnight on Friday of spring break: hardcore. Well done.

    Thursday, March 11, 2010

    PH253: notes on hydrogen

    I scanned the last 4 or so lectures worth of my own notes and put them online. They cover the radial Schrodinger equation, the states of the hydrogen atom, and spin. Today's stuff starts on page 33, for those (many) of you who were not here today.

    Nice pictures of atomic orbitals

    One, two, three

    Tuesday, March 9, 2010

    PH253: hints on HW6-7, #1

    There is one big issue with this problem: there are lots of shiny numbers that you're just dying to plug in to messy equations. Resist! It is a trap!

    PH253: Hydrogen wavefunctions

    Good starter; wavefunctions; probability plots. Hyperphysics is good stuff.

    PH253: Belated HW4 and Exam 1 solutions

    Exam solutions, HW4 solutions.

    The exam solutions are scanned for now, I hope to rectify that situation this week or over the break. HW5 and the quiz/bonus solutions should be out soon as well ...

    Thursday, March 4, 2010

    Wolfram alpha

    If you like the integrator, you'll like Wolfram Alpha. Physics, math, etc. Incidentally, it will do definite integrals numerically, solve cubic equations, and other things useful for the current homework.

    Beware, it is a time sink ...

    Hearing uncertainty.

    Excellent post demonstrating that you can hear wave uncertainty.

    PH253: Supplemental reading for this week & next

    Feynman lectures on physics, volume III, chapter 19. Today we'll cover what's in sections 1-3, which is also covered in your textbook in the appendix to section III.

    Wednesday, March 3, 2010


    UPDATE 2: Fixed. Sorry about that ... should not do these things so late at night I guess. Midterm grades on myBama should now be correct.
    UPDATE: Made a mistake uploading to myBama. Fixing right now. Re-check your midterm grades in about 30 minutes ...

    Moodle grades are now updated. This includes HW1-4, and the exam grade reflects the extra credit from the in-class makeup quiz.* It does not include the extra credit for doing #4b on the test yet ... (Click on the "moodle" tag below to find the instructions for logging in if you have forgotten.)

    Homework and Exam 1 are both worth the same amount in the end, so your overall grade is an average of the two. In the end, I will drop your lowest homework, but I have not done this yet.

    Please check to make sure everything seems to be in order. Wednesday, I'll have to upload midterm grades at some point.

    Also, not doing the homework is really, really hurting some of you.

    * If the in-class quiz did not help your exam grade, it counted toward your overall homework grade. This is not yet reflected in Moodle ... but your mid-term grade will reflect it, and I will try to post those revised numbers soon. This affects only about 20% of you.

    Tuesday, March 2, 2010

    Book contest

    The 4th Annual University Libraries Book Collecting Contest is underway.  The contest is for both undergraduate and graduate students.  Full information about the contest is on the UA Libraries Web site. http://guides.lib.ua.edu/BookCollectingContest

    Monday, March 1, 2010

    Homework 6 & 7

    Homework sets 6 and 7 are combined, and due just as spring break begins. (Don't delay ...)

    There are only 9 problems in this set, but they are a bit more involved, hence its counting twice as much.

    We will go over the problems in quite a bit of detail in the classes leading up to the break.

    UPDATE: re-posted with a few typos fixed and some useful integrals included. Same link above.

    UPDATE: useful, also useful.

    Wednesday, February 24, 2010

    Great physics simulations ...

    Great applets from Univ. Colorado, including some very nice ones related to the quantum mechanics we're doing now. Check out the Quantum Bound States and Quantum Tunneling applets in particular.

    I'll demo a couple of these tomorrow to save you from my crude sketches on the board ...

    PH253: Thursday's quiz

    As I mentioned yesterday, Thursday (tomorrow), there is a quiz.
    • Same material as exam 1.
    • You can bring a formula sheet; same rules as the exam.
    • One problem.
    • The quiz grade will replace the lowest-scored problem on the exam. If you have a very high exam grade, I'll count it toward the homework. It will count toward your lowest non-dropped homework.
    • It will take about 15 minutes.
    • You should study the exam problems. 
    • You can still do 4b from the exam for yet more points.
    • If you are satisfied with your grade so far, you do not have to bother.
    • It will happen at the end of the class period.
    • If you can't make it to class, you should document your reason in some fashion.
    Hopefully that's everything ... let me know if you have questions.

    Tuesday, February 23, 2010

    PH253: Supplemental texts

    If you're looking for some additional reading, I can recommend two more supplemental texts (in addition to the Feynman Lectures on Physics I already recommended):

    One is the Serway book used in PH105 and PH106. If you know someone with the full double volume (it is in the Rogers library too), the last chapters are very much the same as what we're covering now. (Physics for scientists and engineers with modern physics / Raymond A. Serway, John W. Jewett, Jr.). I would guess that it is pretty easy to find someone that has this book left over from PH106, and there should be multiple copies in the Rogers library since it is a book we've used for a long time.

    Another very good book, one I came close to using this semester, is the one by A.P. French (An introduction to quantum physics / A. P. French, Edwin F. Taylor.), which is also in the Rogers library. The mathematical level is at times a bit higher, but the explanations and examples are I think very clear. Some of the problems from your homework come from this book in fact, and I would probably recommend it over the Serway book for understanding the qualitative aspects.

    In similar news, I am going to try to tie the homework problems to each Tuesday's lecture a little more closely so I can spend a larger portion of the in-class time on homework problems. This time around, most of the problems relate directly to stuff that I'll go over in Tuesday's (er, today's) class, and I'll try to make that the case most of the time.

    (Also, as a reminder: if you click on an event in the course calendar (look to the right side of the page), and ask to "show event details," the relevant sections of the textbook for each lecture are listed.)

    Monday, February 22, 2010

    PH255: heavy updates to the lab manual

    Primarily, the procedures for the resistivity/noise (called "rho-mu" in the schedule) and fine structure in atomic spectra now exist. A few other clean-ups as well.

    Additionally, for the resistivity/noise lab you will find useful papers and sample code in the templates directory.

    PH253: HW 5 is out

    Homework 5 is now out. Since I'm a little late in getting it out, you can turn it in Friday instead of Thursday.

    Recall that you can turn in problem 4b from Exam 1 for an additional 1.5 points (5%) on Exam 1. You can turn this in with HW5 (at the latest). 

    Friday, February 19, 2010

    PH253: extra credit

    Tuesday, I'll announce an extra-credit mechanism for you to make up points on the exam. Once I figure out what it is ;-)

    So, rest easy,  and have a good weekend.

    Thursday, February 18, 2010

    PH253: Exam 1 results

    The exam scores are in. You'll get them back in class on Thursday; see the previous post for how to check the scores online.

    There is of course good news and bad news. The good news is that I think most of you are getting the concepts, but there are a few specific points we need to go over. The bad news is somewhat more multi-faceted.

    Checking grades online

    I now finally have the system set up so you can log in and see your grades. Instructions below the jump ...

    Wednesday, February 17, 2010

    PH253: Thursday's class

    That's all for tonight. I should have the exams graded and returned to you on Thursday (along with HW3), given that I finished half the grading after dinner.

    For Thursday's class, we'll go over the exam, and then talk about more solutions to the Schrodinger equation (square well, tunneling). For that, you should finish reading section 2. Next week we'll get to the Bohr model, the start of section 3.

    (About the poll on the right: just for my curiosity. Answer honestly, it is anonymous.)

    PH253: Exam note #3

    Through the first three problems, I am guessing I will have to scale the exam a bit. Number 2 was the best of the three, probably owing to the very similar practice problems.

    One thing to note: the practice problem most relevant (#10) had one mass-less decay product, on the exam question that was not true ... similar problems, but not quite identical. The main difference is that E=pc only works for massless particles.

    On the exam problem, since the decay products were identical in mass, and the parent started at rest, the two decay products must have equal and opposite momentum. Thus, their velocities must be equal and opposite, and their gamma factors the same. If that is true, the two decay products must have the same energy. Energy conservation then equates the rest energy of the parent (Mc^2) with the total energy of the two decay products. Since the two products have the same mass and gamma factor:
    Mc^2 = \gamma_1 m_1c^2 + \gamma_2 m_2 c^2\\M = m \left(\gamma_1+\gamma_2\right) \qquad (\text{since } m_1=m_2\equiv m)\\
    M = 2m\gamma \qquad (\text{since } \gamma_1=\gamma_2\equiv\gamma)\\
    \frac{v}{c} = \sqrt{1-4m^2/M^2}

    PH253: Exam note #2

    On Thursday, it is crucial that we discuss series expansions briefly. Very handy little things that will come up more and more often, and judging from the number of people skipping problem 3, something you haven't been exposed to much.

    Try to remind me of this when we go over the test on Thursday :-)

    Also, I am apparently live-blogging my exam grading. This is deeply strange.

    Tuesday, February 16, 2010

    PH253: Exam note #1

    A quantity like "35000 revolutions per minute" is an angular velocity. Say you have disc spinning at an angular velocity (omega), and you are interested in the linear velocity at a point a radial distance r=0.1m from the center of the disk. The velocity calculation goes like this:
    v = r\omega = \left(0.1\,\text{m}\right)\left(35000\,\frac{\text{rev}}{\text{min}}\right)\left(\frac{1\,\text{min}}{60\,\text{sec}}\right)\left(2\pi\,\frac{\text{rad}}{\text{rev}}\right)\approx 370\,\frac{\text{m}}{\text{s}}

    First, you need to convert the angular velocity to radians per second (or just 'per second' since radians are really just a ratio, and thus unit-less). Then you can multiply by the radial distance from the point of rotation to get the regular velocity or speed at that point on the disk.

    That's my main comment on problem 1 of the exam. The second one being that the time dilation factor is just the ratio between the time elapsed at the rim of the disc to that at the center (which is at rest). The ratio is just (gamma) - we don't need to use the full Lorentz transformation, because there is no significant spatial separation, and we are talking about different parts of the same object.