Exam #4:  Friday, April 27, 2001, 8:30 am in class

Covers all assigned sections of chapters 27, 29-31, but see details below


As always, 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).  Please 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 #13:  Material on HW13 will be covered on the test, through Chapter 31.  The “Voodoo Science” reading will not be on Exam #4, although I may put a question related to it on the final exam.  The bottom line is that everything covered through April 20 will show up on Exam #4, so pay attention to the HW13 questions on chapters 30 & 31.


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.

-        Section 27.8

-        Example 6 on page 904

-        “plum-pudding” model; names of hydrogen line spectra (you don’t have to know what the words Lyman, Balmer, Paschen, etc apply to)

-        Page 918 has lots of formulas.  You should know Eq 30.13; you should know how to use Eq 30.8 & 30.10 if I give them to you.

-        Section 30.5: I won’t ask a question about n, l, m, s or example 5, but you should know the rest of this section.  In particular, angular momentum (formulas 30.15 and 30.16) are nice formulas, and conceptual examples 6 & 7 are nice.

-        Section 30.6


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.


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

-        Air wedges (page 838), Michelson interferometer (section 27.4)

-        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.

-        See above for what you should know from section 30.5

-        Keep in mind the conversion between J and eV


Earlier Material:  Don’t forget how the index of refraction modifies the wavelength of light, useful for thin film problems.  Don’t forget the relationship between c, f, and l for light.


Tricky questions which may be on the exam

-        As emphasized in class, you want to make sure you understand rules #1 & #2 at the top of page 836, about thin film interference

-        Don’t forget that for thin film interference, the wavelength you use is the wavelength inside the film, not the “vacuum” wavelength

-        For 2-slit interference problems, the key is DL; formulas such as 27.1 & 27.2 are approximations that are only valid if the screen is far away.


Office hours:  They are different, unfortunately:

            Tue Apr 24 1 – 5 pm            Emerson 309

            Tue Apr 24 7 – 9 pm            Emerson 363 (as usual)

            Wed Apr 25 1 – 5 pm            Emerson 309

            Thursday:       NONE

Homework #13 is due Wednesday at 5 pm; I will answer questions about this homework right up til 5 pm.  If you cannot make my afternoon office hours, please let me know and I can schedule additional time in the mornings.  I will probably not have email contact on Wednesday evening or Thursday.  Answers to HW #13 will be posted by 6 pm on Wednesday.


Format and grading of exam:  Similar to 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:


-        If you look at a window, you don’t see thin film interference, even though some light reflects off the front face of the window and additional light reflects off the back face.  Why don’t you see interference patterns?

-        In electron microscopes, electrons are used rather than light (photons).  Why do electron microscopes have higher resolution than light microscopes?

-        Describe a situation where electrons act like waves.  Describe a situation where electrons act like particles.


Answers to these questions will be posted on the web page soon.