In Young's double-slit experiment , d is separation between the slits. Separation between plane of the slits and screen is D. Wavelength of light used is `lambda`. Number of fringes per unit distance on the screen is

Options

A. `lambda D//d`
B. `d//lambda D`
C. `lambda d//D`
D. `D//lambda d`

Answer

B

Explanation

Separation between two consecutive fringes is given by fringe width `omega = lambda D//d`. Hence, number of fringes per unit distance is inverse of it.
Number of fringes per unit distance = `1//omega`
`=d//lambdaD`.