Slides on Lasers & Holography

Some slides on lasers from Dr. Kung, and some slides on holography from Prof. Hewitt at Dalhousie University, for your final-exam-studying enjoyment.


(Info on the final will follow very soon. For now, assume it will be a linear combination of the first two exams, roughly twice the length of either.)

This week's lab: spectra

Here you go, something a little bit lighter* for dead week. Our 6th and final lab.

As a reminder, you need to turn in 4 reports for the 6 labs. They are due by the final exam time, and there is not much time left to procrastinate at this point.

(Some of you have turned in lab reports but your lab partners did not. Remind each other about these things.)

*haha

Optics exam 2 solutions

Here you go. Exam 1 solutions to follow soon ...

For Tuesday, group B will have a lab (which I will post this evening) and group A will have a lecture. On Thursday, reverse.

This week

Sorry, I just realized that I inadvertently swapped next week's lectures and this week's. So, we'll talk about holography this week and fiber optics next week.

Exam 2 grades

I've just emailed all of you your exam 2 grades. Apologies for the form letter, but even with a small class this is a tedious task ... if you didn't get a grade emailed to you, let me know.

Overall, it came out well - the average was about 82%, and I think most of you will be relatively happy. The average of the first two exams is about 73%, and in particular many of you that didn't do so well on the first one showed significant improvement. Almost everyone improved, some of you by significant amounts. At this point, we will have to decide if, based on the average exam 1 & 2 scores, any scaling is necessary.

Anyway: well done! Solutions to exams 1 & 2 will show up soon so you can use them to study for the final. Since there is not much new material covered between exam 2 and the final, exam 1 + exam 2 gives you a good idea of what to expect for the final.

Tuesday 19 April

Tuesday, group B will have a lab (procedure) and group A will hear all about fiber optics.

Lab reports

Remember that you need to turn in reports on 4 of the 6 lab experiments for the semester. So far, I've been very happy with the lab reports you've turned in, but I worry that you're going to put the remaining ones off a bit too long ... there is not much time left in the semester.

This is just your friendly reminder that it is that time of the semester again, the time when we all wish we had not put things off :-)

Also, I should point out more clearly that our last few labs followed an inquiry-based method. That is fancy talk for when the professor doesn't quite know what will happen either, and the whole point of the thing is to try and figure something out given the resources you have. As a result, your results for the last several labs may not be as straightforward as you might like, and that is ok! If you did your measurements correctly, analyzed the data the best you could, just do the best you can to explain what happened. It may not fit the nice formulas in the book, and that is partly the point - why didn't it work out? Perhaps the intensity variation within your laser beam illuminated some slits less than others, and your intensity measurements are therefore screwy. Perhaps your gratings are not so simply constructed as the textbook imagines. Could be anything, but if you were careful enough, you can rule out a good many possibilities. Real sciencing is messy and difficult. We're not baking cakes here, and there is no recipe for making it come out perfectly.

Physics extra credit exam

The major field test listed below can get you some extra credit in optics class. Here's how it works:

• +2.5% for attending
• variable extra credit up to +2.5% based on your performance (based on national percentile rank, not raw score)

Details:

The Dept. of Physics & Astronomy would like all Sophomore,
Junior & Senior Physics majors to take the Physics Major Field
Test (MFT) in 2.5 weeks:

** Monday 25 April in 203 Gallalee **

This is an annual event in our program that helps us evaluate
the strengths and weaknesses of our teaching.

You may _START_ the exam any time between

**  3:00-4:00pm    **

You are allowed 2 hours for the exam.

** PLEASE E-MAIL me, Ray White   rwhite@ua.edu     **
** AS SOON AS POSSIBLE IF YOU PLAN TO TAKE THIS EXAM.  **

This exam is an extra credit opportunity for all 200-, 300-,
& 400-level physics & astronomy courses this semester
(in some courses, it may be a required component).

We will also offer a 8GB flash drive to all students who
participate, as well as free drinks and munchies. Additional
awards will be given to the top sophomore, junior, senior scorers.

The Physics MFT is online, consists of 70 multiple-choice
questions, with immediate grading.  Only correct answers are
scored, and there is NO PENALTY for omissions or wrong answers.

We will provide scratch notebooks for you to use (which we will
collect when you are done) and calculators are NOT allowed.

Students may view sample questions online at www.ets.org:
http://www.ets.org/Media/Tests/MFT/pdf/mft_samp_questions_physics.pdf

We appreciate your help in finding where we can improve our teaching !!

If you have any questions, please contact: Ray White, Physics & Astronomy Chair

Cramming

If you feel the need, some relevant sample exercises:

Lasers: know the types, know the physical requirements for a system to exhibit lasing, know the rate equations. See the notes I posted for some of this, as well as your own notes from the lectures (that you obviously attended, seeing as this stuff is on the exam, right?).

Geometric optics: uh, lenses. And mirrors. There is not much more to it.

Interference: know HW5 well, 9.18, 9.24. Know how to solve the 2 slit or 2 antenna problem cold.

Diffraction: 10.3,4,10,26,27,33,41 (some of these are very short)

I'm not suggesting you do all of these in the next 10.5 hours before the exam, but if you glance at them and quickly review the ones you aren't sure of, you would be quite clever.

Lastly, prepare your formula sheet well, since there isn't one on the exam. Actually, there are only a small handful of equations required if you have your wits about you. The rest is math.

Last-minute help

You can find some my notes on lasers from PH253 here. You may want to skim the 'identical particles and statistics' notes for background on the introduction if you're curious, but the core laser stuff starts on around page 7 and is pretty self-contained.

This is not exactly what Dr. Kung covered, but probably close enough for some last-minute cramming ...

Coming shortly: suggested problems to look over at the last minute.

How to clean lenses properly

This goes not just for photography, but optics in the lab, and your glasses.

This week

Tomorrow (Tuesday):
- Group B has a lecture (lasers 2)
- Group A has a lab (interference)

Thursday is exam #2 day (UPDATED):
- Same format as last exam, same rules. Solve 5 of the 6 problems, but this time we'll treat the 6th one as bonus credit if you do all 6.
- 3 of the problems will be: 1 general laser concepts (essay question), 1 more quantitative laser concepts (less essay), 1 geometrical optics (ray tracing type, potentially using formulas). For these, review laser lectures and last exam.
- 3 other problems will be on interference and diffraction. The interference & diffraction questions will be confined to material we covered in lecture. Possible topics include: variants on the double slit, thin film interference, superposition of oscillators/antennas, diffraction gratings, and rectangular or other simple apertures.

Tomorrow

Group A: lecture (lasers 2)
Group B: lab (few slit interference)

There is no procedure for the lab. You will be coming up with the procedure as part of the lab ... but it will be fairly obvious what you need to do!