## Tuesday, August 31, 2010

### PH253 facebook group

### 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.

### PH253: applet for tomorrow's lecture

http://webphysics.davidson.edu/applets/retard/Retard_FEL.html

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).

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.

(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.

Labels:
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## 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.

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.

## Friday, August 27, 2010

### PH253: HW2 is out.

I know you're excited. We'll set up all of these in class to get you started.

## Thursday, August 26, 2010

### 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.

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 ...

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.

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.

Labels:
ph253,
ph255,
series-of-tubes,
unrelated

### PH253: Lecture 2

Tuesday's lecture will cover the following:

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 ...

- Lorentz transformations (relating position, velocity, and time in different frames)
- Space-time diagrams
- Momentum
- Energy
- Force

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.

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.

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

## Wednesday, August 18, 2010

### Link: modern physics lecture notes

There are some nice online lecture notes for a comparable course here.

## 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.

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

## Sunday, August 15, 2010

### 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:

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.

## 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.

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.

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