Lab 8 Prep Package Available

Lab 8 Prep Package
Lab 8 will be a quantitative experiment to determine the angular dependence of the intensity of polarized light transmitted by a polarizing filter. To generate quantitative measurements we will be using the Photometer:


I will be catching a plane right after class, so we will be closing up at 8:30 PM, a little earlier than usual. On Monday, I'll open the lab up an hour early (5 PM) so you can continue any work that was left undone.

Lab 7 Wrap-up

Lab 7 worked even better than I hoped it would, exploring the vector nature of polarization with hand-held plastic polarizing film. One of my goals is to give you enough "touches on the ball" so you can develop a feel for how optical phenomenon behave. You have plenty of experience with balls, wheels, blocks, and so on. But we all have only limited opportunities in everyday life to manipulate light beyond turning on and off a switch. Every now and then just walking around you will see a curious optical phenomenon. I encourage you to "step outside the box" and take a closer look, take the time to come to some conclusions, and thereby add to your experiential base. You may want to carry around a small piece or two of polarizing film in your wallet just to have a fun investigatory tool.

LOL Labz

U r makin' me haz seen the lite!

Lab 7 Materials Available

I've been sent on a lightning trip by my day job to spend Monday morning at an out-of-town vendor, so lab 7 prep has been rather rushed. Even so, I managed to preflight on the table and to put together a simple lab guide. If you have some small transparent plastic items at home, you may want to bring them to class to use them in the last section.
Lab 7 Plan of the Day
Lab 7 Materials
Self-Assessment

Lab 6 Notes on Notebooks

In lab 6 I spent 5-10 minutes one-on-one going over lab notebooks. Some comments:

1. There is a wide range in style.
2. There is a wide range in quality.
3. Not everyone seemed satisfied with their notebooks.
4. Here's a strategy for improving your notebook:
--- Refer to the checklist in the material for Lab 1.
--- Review your notebook against the checklist.
--- Pick an area to improve.
--- Spend extra effort on that area until you see improvement.
--- Iterate.
5. Not many notebooks recorded lab procedures. These are necessary to reproduce a result.
6. Good notebooks can save you in the future from extra work redoing stuff that you just didn't bother to record. Get in the habit of recording everything that makes sense, especially puzzling facts.

I will review lab notebooks in class again. At that time we will make "improvement contracts". In the meantime, use the feedback provided and these comments as an opportunity to improve your practices. Out in the wild you will find it necessary to keep good lab records in order to make reliable progress on a project and be confident of the results.

Lab 7 Prep Package Available

Lab 7 Prep Package
Note that you will design an experiment and write the procedure for executing it. If you have or can borrow some polarizing sunglasses, bring them to class.

Lab 6 Materials Available

Lab 6 Plan of the Day
Your Lab Notebook!
Precision Stage Drawing Tree
Self-Assessment

Lab 5 Fringes - Cell Phone Photos

Here are 3 sets of fringes from the Lab 5 microscope slide experiment, one from each team's successful layout. An incident beam I reflects first off the front surface of the slide creating one reflected beam, and then off the back surface, creating another. These travel almost in the same direction, but not quite, due to the small tilt of surface S1 with respect to S2. This tilt is there because the slide surfaces are not perfectly parallel. The number of fringes and the size of the illumination spot on the slide measure the tilt angle, typically a few mrad.

Reflection geometry. Each reflection is about 4% as intense as incoming beam I. Not shown is the transmitted beam T that continues downward to the left.



The fringe orientation is due to the wedge orientation. In lab we rotated a slide to see that the "clock" angle of the fringes is tied to the slide, not to the rest of the optics.

We also tested what would happen if we overlapped the fringe pattern from one experiment bay on top of the beam from another experiment bay. Additional fringes or no additional fringes? At first sight we didn't see evidence for additional fringing - the pattern looked like the straight addition of the 2 fringe patterns rather than the interference of those 2 fringe patterns. Remember that the number of fringes is related to the angle between the two beams, with about 5 fringes per mrad. The two beams were incident at an angle of several hundred mrad, so there were of order a thousand of these new fringes across the pattern -- too many to resolve since there's more than one fringe per camera pixel. So we didn't see much new. If we had inserted some clever optics to overlay the two beams with a small, mrad sized, angle between them (like is done when you use 2 stacked slides), then what would we have seen at the detector/screen?