Differences between law of flotation and Archimedes's principle

Explain vector addition, triangle method and parallelogram method

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?

The total amount of energy contained in an object