Exam #3:  Friday, March 30, 2001, 8:30 am in class

Covers all assigned sections of chapters 24-26, but see details below


This handout is an attempt to give you a sense of what’s important to study for and what’s less important.  However, ultimately you are responsible for the reading material (even if not discussed in class) and the material covered in lecture (even if not in the reading).  If you missed any lectures, try to get the notes from someone who was there.  You are welcome to ask me questions about anything you didn’t understand.


Notecard:  You are allowed a 4”x6” card with any notes you care to write on it, both sides.


Homework #9:  Material on HW9 will be covered on the test; lenses are fairly similar to mirrors so all of HW9 is potential exam material.  Note that after the Friday Mar 23 lecture, we will have covered most of the material necessary for that homework.  So, you should have plenty of time to figure out what is confusing, and learn it before the exam.  I plan to have the solutions on the web page by 5 pm Thursday, so please try to look at them that evening.


Stuff not on exam:

-        Prefixes like “micro” or “nano” – you should know these, but if I use them on the exam I will remind you what they mean.

-        Antennas & section 24.1

-        Energy density (first part of section 24.4; you DO need to know about intensity)

-        Ray tracing

-        Section 26.14 – will be on final exam though


Stuff that will be on the exam:  Previous homework, suggested problems, and problems/concepts discussed in lecture are the highest priority.  Try not to merely memorize solutions, but to make sure you understand how to set up problems.  Chances are good that there will be a problem on section 26.9 (lenses in combination).


Stuff you shouldn’t overlook – topics that may not have been emphasized but which you should know something about:

-        We’ve covered a lot of tiny topics:  for example, index of refraction & speed of light, Snell’s Law, Brewster angle, critical angle, Doppler effect.  It is likely there will be tiny questions covering each of these topics.

-        Be sure you know the relationships between wavelength & frequency of light, the speed of light, and how these are related to the index of refraction.


Earlier Material:  If antennas were on this exam, you’d need to know something about resonant circuits.  Since they’re not on this exam, you don’t need to know any of the earlier material.


Tricky questions which may be on the exam

-        For polarizer problems:  there is a big difference if the incoming light is polarized, or unpolarized.  Be sure you check what the incoming light is.

-        For Snell’s Law, the angles are measured from the normal – be wary of problems which give you information about other angles.  Just because it’s called “theta” doesn’t mean an angle is what goes into Snell’s Law!  The same holds true for polarizers & Malus’s Law.  Hopefully the problems on HW8 have made that clear (at least for polarizers).

-        Keep in mind you need to know the definitions of the words “convex” and “concave” when describing mirrors.


Office hours:  As usual, plus additional office hours 2 – 6 pm on Thursday (with a short break for me from 2:50 to 3:20).


Format and grading of exam:  Similar to previous exams; however, if there are multiple choice questions, they will be worth less than they have been on previous exams.  On the test, if you are pressed for time, at least write down the correct equations, draw a diagram if appropriate, and indicate how to get the solution – this will get you substantial partial credit if you are writing down correct things.  Writing down incorrect or random formulas will not help you, but otherwise it’s easy to get partial credit.


Some additional concept questions to help you review:


-        When we went outside with the polarizers, it was cloudy and the sky was not polarized.  Still, we saw lots of polarized light in different places.  Where did that polarized light come from?


-        I have a flashlight and I want to produce some polarized light.  Which produces polarized light of a higher intensity: (1) sticking a polarizer onto the flashlight, or (2) reflecting the light off a piece of glass, at Brewster’s angle?


-        If you look at a fish in a pond, the apparent depth of the fish is less than the actual depth, as discussed in class and in the book.  Suppose you look at a fish inside a spherical fish tank; the curvature of the sphere changes things somewhat in a way we haven’t discussed in class (partially a lens effect, partially the depth effect).  Is the image of the fish you see real or virtual?  Since we haven’t discussed this before, you don’t have the relevant equations, but you don’t need them to answer this question.


-        How could you estimate the radius of curvature of a spoon, from the optical properties of the spoon?