Issued Wed, Aug 27 Due Wed, Sept 3

Required reading for this week: Gas. Ch. 1, start Ch. 2.

Here, and throughout the semester, please show your work on all problems. Organize your homework so the grader can follow your solution clearly. Explain (in words) what you're doing and what assumptions you make, whenever it seems appropriate.

There are HINTS for this homework.

1a) Gasiorowicz ("Gas") 1-12a tells you how much energy you find per unit volume inside a black body cavity, in terms of the fundamental constant . Gas. 1-12b tells you how much power leaves a black object per unit area, per unit time. Assuming his number for "a" is correct, use Gas. eqn 1-1 to figure out , numerically. (I claim Gas' number for , which he quotes right after eq'n 1-12b, is off by a few percent)

b) Assume the sun is an ideal black body (it's not a bad assumption!) with radius cm, distance to earth cm, and delivering erg/(cm^2 s) to the surface of the earth at high noon. (This last number is called the "solar constant", and is useful e.g. for estimating the required size of solar panels on your house). Estimate the surface temperature of the sun.

2a) Suppose you do a photoelectric experiment, and find the maximum energy of photoelectrons ejected from a potassium sample is 1.4 eV for radiation of 3500A, and 2.0 eV for radiation of 3000A. Use these data to calculate Planck's constant, and also the work function of potassium. (Be careful not to implicitly assume a value for Planck's constant anywhere in your solution)

b) Suppose in this experiment your 3000A light source has intensity 0.1W/m^2, and your potassium sample is a square 1cm on a side. Not every incident photon will cause a photoelectron to jump out (many will be absorbed, or bounce off) -- suppose only 1% of the incident light ends up creating photelectrons. How many electrons are ejected each second?

3) A 250 keV photon hits a free electron at rest. The photon is scattered through 90 degrees. What is the energy of the photon after the collision? What is the kinetic energy (in eV) of the electron after the collision? What is the direction of the recoiling electron?

4) Gas. problem 1-13

5) Gas. problem 1-15

(Because of Labor Day, no problem from Ch. 2, but start reading it)