tag:blogger.com,1999:blog-22822940168263268782024-03-13T13:20:02.104-05:00Modern Physics @ UAPH255
Spring 2011pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.comBlogger241125tag:blogger.com,1999:blog-2282294016826326878.post-22475757796804303402011-02-07T16:21:00.000-06:002011-02-07T16:21:43.318-06:00Lab schedule<div dir="ltr" style="text-align: left;" trbidi="on">For your reference:<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/_JMsUTJFOJ1E/TVBwYkDIVOI/AAAAAAAAAa0/1gb6rlbd8Lo/s1600/sched.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="201" src="http://3.bp.blogspot.com/_JMsUTJFOJ1E/TVBwYkDIVOI/AAAAAAAAAa0/1gb6rlbd8Lo/s640/sched.png" width="640" /></a></div></div>pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-5902048589483598882011-01-24T01:09:00.000-06:002011-01-24T01:09:54.932-06:00PH255 Lab Manual<div dir="ltr" style="text-align: left;" trbidi="on"><a href="http://faculty.mint.ua.edu/%7Epleclair/PH255/lab_manual/ph255_lab_manual.pdf">Here is the PH255 lab manual [49Mb PDF]</a>, with procedures for all experiments, the syllabus, and plenty of other useful information. You don't need to print anything out before class, I will have the lab procedures printed for you when you arrive. Please read the syllabus, course information, safety rules, and other introductory material as soon as possible.</div>pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-65249328143332739982011-01-13T13:10:00.002-06:002011-01-13T13:10:29.476-06:00UGrad research conferenceRESEARCH AND CREATIVE ACTIVITY CONFERENCE APPLICATIONS — Faculty are requested to remind undergraduate students of all majors that they are invited to enter UA’s annual Undergraduate Research and Creative Activity Conference scheduled for April 11 at the Bryant Conference Center. Students can compete for cash prizes and earn practical experience in defending or performing their work before judges. To participate, undergraduate students must register their projects by submitting application forms and abstracts describing their projects by March 7. Visit http://www.osp.ua.edu/UndergradResearch.html for an application and details.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-47595760816731767152010-12-14T00:45:00.000-06:002010-12-14T00:45:12.052-06:00PH253 final grades, mark 2After 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.<br />
<br />
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.<br />
<br />
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. <br />
<br />
*I didn't revise anyone's grade downward. If there was a grading error in your favor, it stayed.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-14784994207832463952010-12-13T02:27:00.001-06:002010-12-13T02:27:59.507-06:00PH253: preliminary grades on myBamaI've posted "final" grades on myBama, subject to the following qualifications:<br />
<ol><li>I have to check my spreadsheet thoroughly to be sure all my calculations are correct.</li>
<li>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).</li>
<li>Some of you might still sneak in an extra-credit assignment or late HW by the end of Monday. (HINT)</li>
</ol>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.<br />
<br />
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. <br />
<br />
Anyway, I hope you enjoyed the semester, I certainly did.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-41924647211694237492010-12-09T23:03:00.001-06:002010-12-09T23:04:33.624-06:00PH253 Final exam pro tipPro 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.<br />
<br />
I say that since I'm seeing that same mistake again & again on HW9 ... the second problem was <i>nearly</i> like one from last year, but the second part was different in a crucial way. By "different" I mean "not even remotely close."<br />
<br />
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.<br />
<br />
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.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-23957904195916596502010-12-09T09:40:00.004-06:002010-12-09T11:54:02.510-06:00PH253: server issuesUPDATE 2: with the server being down, Moodle is also down until further notice. Hopefully it will come back up some time today. Also, <a href="http://bama.ua.edu/%7Epleclair/PH253/Exams/formulas.pdf">a draft of the formula sheet for the final</a>. <br />
<br />
UPDATE: HW and Exams mirrored <a href="http://bama.ua.edu/%7Epleclair/PH253/">here</a>. The additional notes as well (well, most of them, until I hit my quota on bama.edu. Lame.)<br />
<br />
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:<br />
<blockquote>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.</blockquote>I will try to get a mirror up later this morning.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com7tag:blogger.com,1999:blog-2282294016826326878.post-18693849667448406362010-12-09T01:13:00.001-06:002010-12-09T01:14:17.016-06:00PH253: HW10 solutionsI 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.<br />
<br />
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.<br />
<br />
Of course, that idea was hopelessly naive, and probably just punishes the people who need the most help. <br />
<br />
<a href="http://faculty.mint.ua.edu/%7Epleclair/PH253/Homework/HW10_SOLN.pdf">So, here are the HW10 solutions</a>. I will still accept HW10 up through the final exam, minus the usual late penalty. Remember that I drop the lowest homework.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-70337569032300486042010-12-09T00:11:00.001-06:002010-12-09T00:11:59.123-06:00PH253: 8am exams suck and we can't do a thing about itSo 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:<br />
<ol><li>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.</li>
<li>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.</li>
<li>Don't bother memorizing stuff. I want to see if you can think & solve problems, so you'll have all the formulas you need.</li>
<li>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.</li>
<li>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.</li>
<li>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).</li>
<li>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 ...</li>
<li>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.</li>
</ol>As I have more random work-avoiding thoughts, I will post them here ...pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-29815626607812084182010-12-08T23:05:00.004-06:002010-12-08T23:19:12.244-06:00PH253: Exam 2 solutionsJust realized today after one of you emailed me that I never posted Exam 2 and its solution.<br />
<br />
<a href="http://faculty.mint.ua.edu/%7Epleclair/PH253/Exams/Exam_2/">Here you are</a>. Let me know if you find any errors or need further clarification on any problems.<br />
<br />
Also, <a href="http://faculty.mint.ua.edu/%7Epleclair/PH253/Exams/Spring_2010/Final/">last semester's final with solutions</a>.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com2tag:blogger.com,1999:blog-2282294016826326878.post-11102554691499308432010-12-08T11:30:00.001-06:002010-12-08T11:38:55.658-06:00PH253: final examI've decided to make it easier on you for the final, at least in terms of what you need to study.<br />
<br />
The final exam questions will be drawn <i>entirely</i> 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.]<br />
<br />
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.<br />
<br />
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.<br />
<br />
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.<br />
<br />
And, as a reminder, the final is this Friday at 8am in the usual room.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-54132737546445688332010-12-03T11:22:00.000-06:002010-12-03T11:22:48.217-06:00PH253: HW10 #2Here are a couple of hints.<br />
<a href="http://www.blogger.com/goog_1270624962"><br />
</a><br />
<a href="http://britneyspears.ac/physics/dos/dos.htm">Hint the first</a>.<br />
<a href="http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/eedens.html#c1">Hint the second</a>.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-21716713667234277152010-12-02T01:18:00.001-06:002010-12-02T12:35:01.101-06:00Slides for 2 Dec 2010 lectureUPDATE: the revised slides I actually used are at the same link below. Not many changes.<br />
<br />
Here is an outline of tomorrow's lecture. <a href="http://faculty.mint.ua.edu/%7Epleclair/PH253/Notes/info_storage.pdf">My first draft of the slides are here</a>, 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.<br />
<br />
The outline, as of now:<br />
<ul><li>basic computer architecture</li>
<li>memory </li>
<ul><li>reminder: how transistors work</li>
<li>FLASH memory</li>
<li>S/D/MRAM basics </li>
<li>memory architecture</li>
</ul><li>logic & computation </li>
<ul><li>how to implement logic & computation</li>
<li>logic gates </li>
<li>building gates from transistors/switches</li>
<li>computation example: comparison, addition</li>
</ul><li>information physics</li>
<ul><li>energy requirements & thermal stability</li>
<li>mechanical, electrical, and magnetic storage</li>
<li>losses per cycle</li>
<li>the safety of Moore's "law" and fundamental limits</li>
</ul><li>Time permitting (probably not): hard disks</li>
<ul><li>overview of operation</li>
<li>media (analogous to CD/vinyl)</li>
<li>reading & writing</li>
<li>positioning & mechanical</li>
<li>why magnets?</li>
<li>history & recent boom times</li>
<li>fundamental limits approaching</li>
</ul></ul> No, this is not on the final.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-9720552694077882722010-11-30T23:08:00.000-06:002010-11-30T23:08:30.048-06:00PH253 last lecture: computer logic & memoriesIt 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 ;-)<br />
<br />
The rough plan will be this:<br />
<ul><li>What is our current high-level computer architecture?</li>
<li>How does one make memory/logic? What components are required? How do they work?</li>
<li>How do we currently build logic and memory? </li>
<li>How do (s/d)-ram and flash memories work? </li>
<li>What are the future prospects/promising new technologies?</li>
<li>Is Moore's "law" really in trouble? (Spoiler: it is not a law, and not yet.) </li>
</ul>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:<br />
<ul><li>A brief overview of how hard disks work</li>
<li>A brief overview of how mram might work (spoiler: it isn't ready yet)</li>
<li>Energy requirements/limitations for computation</li>
</ul>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).pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-88364945331712643802010-11-30T01:57:00.000-06:002010-11-30T01:57:50.858-06:00Tuesday's lecture, evaluationsToday, in about 10 hours, we will figure out how <a href="http://en.wikipedia.org/wiki/Dr._Evil#Schemes">lasers work</a>. That's our last regular lecture, Thursday's lecture is <a href="http://ph253-255.blogspot.com/2010/11/ph253-last-lecture.html">still up to you</a>, to an extent.<br />
<br />
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.<br />
<br />
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.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-24060882044942012412010-11-30T01:47:00.000-06:002010-11-30T01:47:51.930-06:00PH253: Final ExamNote 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.<br />
<br />
Basic rules:<br />
<ul><li>12 problems, you choose 6 to solve.</li>
<li>If you do more than 6, I'll grade the best 6.</li>
<li>Comprehensive - basically <i>everything</i> <i>through last week</i> will be on the exam (i.e., nothing on this week's lectures).</li>
<li>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.</li>
<li>You can bring 2 of your own sheets of 8.5x11 paper, double sided (or 4 sheets single sided). </li>
</ul>Topics, roughly<br />
<ul><li>Relativity</li>
<li>Radiation (accelerated charges, blackbody)</li>
<li>Photoelectric/Compton/photons</li>
<li>Wave-particle; de Broglie</li>
<li>Schrodinger's equation, 1D potentials</li>
<li>Bohr atom</li>
<li>Hydrogen in 3D</li>
<li>Angular momentum & spin</li>
<li>molecules & bonding </li>
<li>Multi-electron atoms & the periodic table</li>
<li>periodic solids, energy bands, metals-insulators-semiconductors</li>
<li>particle statistics</li>
</ul>Definitely not on the final, but covered in class:<br />
<ul><li> LASERs</li>
<li>variational method</li>
<li>p-n junctions (diodes), transistors</li>
<li>whatever we do for the last lecture</li>
</ul>Gaming the system:<br />
<ul><li>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. </li>
<li>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.</li>
<li>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.</li>
<li>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 <i>sorts</i> of problems I have before, if not the same thing exactly.</li>
<li>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.</li>
<li>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.</li>
</ul>pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-43057726180792969592010-11-30T01:30:00.001-06:002010-11-30T01:31:03.401-06:00PH253: one more extra-credit possibilityOne last chance for extra credit, the procedure is much like the last time. Due at the start of the Final exam.<br />
<ol><li>You watch <a href="http://research.microsoft.com/apps/tools/tuva/index.html#data=3%7C%7C%7C">one of these lectures</a> (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.***</li>
<li>You write me <b>3 page</b> (8.5x11 in paper, 1.5 inch margins, 12pt font, single spaced) paper covering</li>
</ol><blockquote><ul><li>Two new things you learned from the lecture (or things you understood better)</li>
<li>One way the lecture tied in to PH253</li>
<li>One way the lecture tied in to your major/field of study</li>
<li>One way the lecture tied in to everyday life</li>
</ul></blockquote>Do this, and I give you as much as +2% on your <i>overall</i> 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.<br />
<br />
To give you an idea of what 2% means:<br />
<ul><li>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 :-)</li>
<li>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.</li>
</ul>*If you are a non-native English speaker, this will be taken into account. English grammar and spelling is very silly.<br />
**More like 'at least 2.7', since 30% of your PH253 grade is still to come ...<br />
***Also, thanks to Bill Gates for making these lectures available ...pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com4tag:blogger.com,1999:blog-2282294016826326878.post-33930761604119582422010-11-30T00:42:00.002-06:002010-11-30T00:42:24.843-06:00PH253: more grades on MoodleJust uploaded HW8 grades, which leaves only HW9 outstanding at the moment. I'll try to have that by the end of the week.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-31439609383871331412010-11-23T13:09:00.001-06:002010-11-23T13:10:11.089-06:00PH253: last lectureWe 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. <br />
<br />
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.<br />
<br />
My own suggestions, in no particular order:<br />
<ul><li>more on transistors & semiconductor electronics</li>
<li>information storage technologies (hard disks, ram, flash, etc.)</li>
<li>two-level systems & resonance</li>
<li>applications of particle statistics (chemical kinetics, diffusion, etc)</li>
<li>crystals, geometry, & diffraction</li>
<li>magnetic materials</li>
</ul>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.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com6tag:blogger.com,1999:blog-2282294016826326878.post-48340628913610794002010-11-23T12:54:00.000-06:002010-11-23T12:54:44.942-06:00PH253: notes from todayToday's lecture was mostly drawn from the Feynman lectures, vol III, ch. 3-4. My own notes from last semester are <a href="http://faculty.mint.ua.edu/%7Epleclair/PH253/Notes/Spring_2010/identical-particles_statistics.pdf">here</a>. (I didn't change much this time around.)pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-39888402085525471912010-11-22T23:23:00.000-06:002010-11-22T23:23:36.132-06:00Student opinions of instructionReminder, you should be doing your course evaluations (student opinions of instruction, or SOI) right about now.<br />
<br />
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).pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-38727060679833471852010-11-22T13:48:00.000-06:002010-11-22T13:48:28.842-06:00PH253: last homework set<a href="http://faculty.mint.ua.edu/%7Epleclair/PH253/Homework/HW10.pdf">Here you go.</a> 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.<br />
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Keep in mind I drop one homework set, so if you've done them all so far ...pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com2tag:blogger.com,1999:blog-2282294016826326878.post-26407643632735451392010-11-16T01:05:00.000-06:002010-11-16T01:05:31.100-06:00PH253: HW8 & 9 solutions<a href="http://faculty.mint.ua.edu/%7Epleclair/PH253/Homework/">Partial HW8 solutions (numbers 1-4 only have answers) and full HW9 solutions (rather detailed) are out now</a>.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-57113742125280947352010-11-15T00:27:00.002-06:002010-11-15T00:27:36.620-06:00PH253: Moodle grade update<a href="http://faculty.mint.ua.edu/%7Epleclair/moodle/">Moodle</a> is up to date through HW7 now (as well as including late HW and exam 2 alterations).pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0tag:blogger.com,1999:blog-2282294016826326878.post-58627158049789022042010-11-10T00:40:00.000-06:002010-11-10T00:40:57.734-06:00PH253: what is the point of HW9?This week's homework is difficult, I grant you that, but not without reason.<br />
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*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.<br />
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* 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.<br />
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* 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).<br />
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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.pleclairhttp://www.blogger.com/profile/07263994015241270268noreply@blogger.com0