[SOLVED] X-ray reflection/Bragg's law help??

freefallin38

1. The problem statement, all variables and given/known data
The planes of atoms in a cubic crystal lie parallel to the surface, 0.81 nm apart. X rays having wavelength 0.37 nm are directed at an angle θ to the surface.

(a) For how many values of θ will there be a strong reflection?
4
(b) What is the largest value of θ that gives a strong reflection?

(c) What is the second largest value of θ that gives a strong reflection?

(d) What energy electrons could give the same result?



2. Relevant equations
Bragg's Law n[tex]\lambda[/tex]=2*d*sin[tex]\Theta[/tex]


3. The attempt at a solution
So I guessed for the answer for part a, I found some things online that had 4 angles, but I have no idea how to find the angles?? Can anyone explain to me what a strong reflection actually is and how to find it?