When it is summer at the south pole,
a. the northern hemisphere is tilted toward the sun.
b. both the southern and northern hemispheres are tilted toward the sun.
c. the southern hemisphere is tilted away from the sun.
d. the northern hemisphere is tilted away from the sun.

The nuclear potential that binds protons and neutrons in the nucleus of an atom is often approximated by a square well. imagine a proton conned in an innite square well of length 105 nm, a typical nuclear diameter. calculate the wavelength and energy associated with the photon that is emitted when the proton undergoes a transition from the rst excited state (n 2) to the ground state (n 1). in what region of the electromagnetic spectrum does this wavelength belong?