Issued Wed, Jan 31 Due Wed, Feb 7

Required reading: F+T All of Ch. 1 (Optional Beiser 4.3-4.6, 4.8)

1a) F+T 1.4

1b) Gold has Z=79, A=197, and density about . Knowing Avogadro's number, estimate the approximate size of a gold atom.

(Here's a bad joke. What's a guacamole ?)

2) F+T 1.13 (parts a and b only)

3 a) What is the impact parameter, b, of a 5.0 MeV alpha particle that is scattered by 5 degrees when it approaches a gold nucleus?

3b) Show that the probability for a 2.0 MeV proton to be scattered by more than a given angle when it passes through a thin foil is the same as that for a 4.0 MeV alpha particle.

4a) What fraction of a beam of 5.0 MeV alpha particles incident upon a gold foil 400 nm thick is scattered by more than 90 degrees?

4b) Alpha particles with a speed of 0.1c are scattered from this same gold foil. If the distance from the foil to the screen is 10 cm, and a million alphas have struck the target, find the number of incident alpha particles which have struck the screen (per square cm) at a scattering angle of 90 degrees.

Hint (See #1b for some useful properties of gold)

5a) How many different wavelengths appear in the spectrum of hydrogen atoms initially in the n=4 state? (why?)

5b) How much energy is required to remove an electron which is in the n=4 state from a hydrogen atom?