The files gratingA1.pdf and gratingA2.pdf contain plots (for the same situation
just for different ranges of y) of the light intensity vs y for the basic
situation of problem 35-32: screen location D=4m, slit separation d=4.5�m with y
representing the coordinate (in meters) along the screen.
In this case the optical element is a grating with N slits, each of width a,
separated by distance d. Using these plots find: (A) the wavelength of light,
(B) the slit width a, and (C) the number of slits N.

old exam #5:
http://www.physics.csbsju.edu/211/2006/211t2_06.pdf