One can picture the importance of amount and direction when imagining the
childhood experiment with the flashlight and orange. Usually this is to depict
the light intensity of “the sun” (the flashlight’s rayon different parts of the
planet. It can also be used to explain how rounded solar energy sensors can pick
upangled rays better than a flat sensor (like if the flashlight were shown on a
sheet of paper, straight on, and then from an angle.) Since, regardless of the
angle, the sphere would always receive part of the ray “directly”, but the flat
sheet of paper would receive the ray as the amount of light times the cosine of
the angle (from perpendicular).This quantity is called the photon irradiance.
Irradiance = (A) x cosine (alpha)