In Young's double slit experiment the amplitudes of two sources are `3a` and `a` respectively. The ratio of intensities of bright and dark fringes will be

Options

A. (a) `3:1`
B. (b) `4:1`
C. (c) `2:1`
D. (d) `9:1`

Answer

B

Explanation

`(I_(max))/(I_(min))=((a_1+a_2)/(a_1-a_2))^2=((3a+a)/(3a-a))^2=4/1`