What is the correct reference frame for a given situation?

The difference between a red shift and a blue shift has to do with wavelength frequency. t or f

Light traveling in water, nwater = 1.33, strikes a plastic block at an angle of incidence of 51.4°; part of the beam is reflected and part is refracted. if the index of refraction of the plastic is 2.0, what is the angle made by the reflected and refracted beams?

What type of force holds atoms together in a crystal?