Homework Help: Fresnel diffraction

1. Nov 6, 2009

avisha03

1. The problem statement, all variables and given/known data

The sun is 45 [deg] above the horizon.
A wall, 10 [m] height is penpandicular to the line sun-earth. Compute the luminous flux, under the following conditions:
1. The geometric shadow, while the sun angular dimension is 0.5 [deg].
2. Fernsel diffraction- the sun as a point source.(lambda=500[nanom])

2. Relevant equations

Fresnel integrals

3. The attempt at a solution
I did question 1, under the estimtions of the sun distance>>the geometric shadow, and got a nice pattern when the flux is zero until the first ray can reach the floor, gets higher until a full sun flux can reach the ground.
I'm not sure how to relate the second question. If the ray is passing right near the wall- the flux must be zero- since fernsel integrals are equal to 0.5 on infinity (we relate the point nearest the wall as the infinity, and the infinite distance as the zero ). how can I compute the pattern?
Thanks alot.