PH253: practice problems have solutions.

Same link as before, here.

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 ...

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.

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)

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.

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 ...

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
scores.

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?

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 ...

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.

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!

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.

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:

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
Molecules
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.

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.)

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: