Please help! Thanks so much! :)

Amplitude is a measure of a waves a; speed b; distance c; energy d; frequency

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?

Give one example to show that when substances are mixed,it may result in a chemical or a physical change depending on the conditions.