Question

White light strikes a diffraction grating (645 lines/mm) at normal incidence. What is the highest-order visible maximum that is formed? Express your answer to the nearest integer.

Answer 1

Number of lines on the garting per one meter is, N=64.5x10-4 m- Grating equation is, d sin =m2 d sin e m = m is the order of the diffration pattern. incident light visible light its range is 400 nm to 700 nm as smallest wavelenght will result highest order of maximum (2=400 nm) and N = d sin e 1. max = T G sino sin Ꮎ IN sin 90° (400x10-9 m)(64.5x109 m) = 0.0038x10-3 = 3.8 (complete number only considered visible order) 3 Therefore, highest-order visible maximum that is 3