`M_(1)` and `M_(2)` are plane mirrors and kept parallel to each other. At point O, there will be a maxima for wavelength `lambda`. Light from a monochromatic sources S of wavelength `lambda` is not reaching directly on the screen. Then, `lambda` is

Options

A. `(3d^(2))/(D)`
B. `(3d^(2))/(2 D)`
C. `(d^(2))/(D)`
D. `(2d^(2))/(D)`

Answer

b

Explanation

The situation can be taken as if there are two sources `S_(1)` and `S_(2)` as shown in the figure in question.
For 'O' to be a maxima:
Path difference `((3d)(d // 2))/(D) = (3d d)/(2D) = n lambda`
` implies lambda = (3d^(2))/(2n D)` or `lambda = (3d^(2))/(2 D)`