What was the kinetic energy of a 2-kg plate that falls from 15-meters and right before it hits the ground? a. 225 joules b. 15 joules c. 300 joules d. not enough information given

So we want to know what is the kinetic energy of a plate with mass m=2 kg that falls from height h=15 m. So initially the plate has potential energy Ep=m*g*h=294.3 J. That potential energy converts completely into kinetic energy right before the plate hits the ground. Our answer is close enough to 300 J so the correct answer is c. 300 Joules

The oscillations producing a light wave are "normal" to the direction of the energy transferred by the light wave. Hope that helps.