A photon of wavelength 0.14800 nm, traveling due east, is scattered by an electron initially at rest.

Question:

A photon of wavelength 0.14800 nm, traveling due east, is scattered by an electron initially at rest. The wavelength of the scattered photon is 0.14900 nm and it moves at an angle q north of east.
(a) Find θ.
(b) What is the south component of the electron's momentum?