Question

A grating has 16000 per inch over a length of 5 inches. What will be the smallest wavelength difference for a light of wavelength 6000 Å?

(a) 0.01 Å

(b) 0.02 Å

(c) 0.03 Å

(d) 0.04 Å

The question was asked in an interview for internship.

This key question is from Plane Diffraction Grating in division Diffraction of Engineering Physics II

Answer 1

Right choice is (c) 0.03 Å

To explain: N = 16000 X 5 = 80000, n = 2

Wavelength = 6 X 10^-5 cm

Resolving power = nN = 2 X 80000 = 160000

Smallest wavelength difference = λ/nN

= 0.0375 Å.