Dear all: If I have a white light source which is at the positive infinite, and there is a plane receiving the light. Assuming that the plane is facing to the light source at the beginning. If I start rotating the plane, and keep recording the intensity of one point of the plane, what function can model the change of the intensity change please? Assume that: 1. The intensity was 1 initially, and 0 if no light comes to it. 2. Mirror reflection 3. rotate from 0 degree to 180 degree Intuitively I feel like cosine function can model the curve, is it correct??? Could anyone give me any hint please? It would be grateful if someone direct me to some books or papers please??? Thanks!!!!