Question

Diffraction Gratings Consider a light with wavelength, of 800nm hitting a transmission diffraction grating with 1200 slits/mm. a. What is the spacing between individual slits in the diffraction grating? b. Draw this in a diagram of this situation. Note: Bright Fringes that diffract at an angle > 90 degrees will never hit the viewing screen, no matter how wide it is. c. Use this fact to determine how many bright fringes in total that can be expected to be seen after the light passes through the diffraction grating for part a. d. Imagine that we want to stop these bright fringes from spreading out by placing a converging lens one focal length away from the diffraction grating. For this to occur the lens needs to be wide enough to collect the highest order fringe on each side of the center. If the focal length of the lens is 20mm, what diameter will the lens need to be to stop these bright fringes from spreading?

For a like, provide both mathematical and written explanations of the answer to each part.

Answer 1

h Given N= 1200 slits/mm spacing or slit Width da to Imm Th 1200 gd= 8.333 xiom spacing @_89.834 LE SIT Hн: ННІ € ad sine = ni sino = a b {

= 2. » Ток к а/, nman I 83.35X108 800 x 69 Inmar I 1.0416 I nmax a 1 ffff įre 0 = 73.73° k raf tan @ = 0.068 m diameter =D = ar 7 D = 0.1371 m D = 13.21 Cm7