As shown in the figure, a given force is applied to a rod in several different ways. In which case is the torque about the pivot P due to this force the smallest?

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?