7650 program 3

Assume the sensor is in the z=0 plane and its width is arranged from -1 to 1 and
it's height is between -(ny/nx) to (ny/nx).  Emit photons uniformly from a sphere
with radius 0.1 and with center (0,0,0.1) and a uniform spectrum E(lambda) = constant.

SO for each photon:
   1. pick a random location on the sphere
   2. pick a random direction away from the sphere
   3. pick a random wavelength
   4. if the photon hits the sensor, do the same thing as in program 2