Question

Which of the following is the correct expression for the ratio of the intensity of principal maxima to the intensity of secondary maxima?

(a) 1 + (N^2-1) sin^2β

(b) 1/1 + (N^2-1) sin^2β

(c) (N^2-1) sin^2β

(d) 1/(N^2-1) sin^2β

The question was posed to me in semester exam.

My enquiry is from Plane Diffraction Grating topic in chapter Diffraction of Engineering Physics II

Answer 1

Correct choice is (a) 1 + (N^2-1) sin^2β

Easy explanation: The expression 1 + (N^2-1) sin^2β is the relation for the ratio of the intensity of principal maxima to that of the secondary maxima. It shows that the intensity of secondary maximas are inversely proportional to N.