An 18 mm wide diffraction grating has rulings of 710 lines per mm.Light is incident normally on the grating.Monochromatic light of 506 nm wavelength is used.The largest angle from the normal at which an intensity maximum is formed is closest to:
A)46°
B)44°
C)42°
D)40°
E)38°

Question

Quizplus · Accepted Answer

The diffraction angle θ for the maximum intensity is given by the grating equation: d*sin(θ) = m*λ, where d is the distance between adjacent lines (1/710 mm), λ is the wavelength (506 nm), and m is the order number. The largest angle corresponds to the highest possible m for which sin(θ) ≤ 1. Calculating for m = 25, θ is approximately 46°.

An 18 Mm Wide Diffraction Grating Has Rulings of 710