# Function to model intensity change over rotation

1. Apr 12, 2009

### Asuralm

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!!!!

2. Apr 13, 2009

### buffordboy23

This sounds like a homework problem. This problem is not well stated in my opinion, but here are some hints to get you thinking.

Since the light source is at an infinite distance, what approximation can we assume for the EM wave incident on the plane? Also, as the point rotates with the plane (which, in general, causes the point to approach or to recede from the light source), is the variation in intensity significant to consider?

How large is the plane? Is it an infinite plane? In the case that the plane is small compared to the infinite distance, imagine the plane as a square loop. How does the electric flux change as we slowly rotate this plane?