Due Wed, Feb 8

Reading for this week: F+T Chapter 1.4, 1.5, 1.7-1.13

(Optional: Beiser (5th ed) Ch. 4.1-4.6)

1) F+T 1-4

2) F+T 1-5

3) F+T 1-13 (a and b only)

4 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?

b) 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?

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

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

6) Extra Credit!

When an excited atom emits a photon, the linear momentum of the photon must be balanced by the recoil momentum of the atom. As a result, some of the excitation energy of the atom goes into the kinetic energy of its recoil. Modify the energy conservation equation:

initial electron energy - final electron energy = photon energy

=

to take this recoil effect into account. (The excitation energy, is a fixed quantity) Call the mass of the atom, M) (Answer is

b) Find the ratio between the recoil energy and the photon energy for the n=5 -> n=1 transition in hydrogen, for which is 13.1 eV. Is the effect a major one?