In a biprism experiment, the fifth dark fringe is formed opposite to one of the slits. What is the wavelength of light?

Options

A. `d^(2)/(3d)`
B. `(d^(2))/(9D)`
C. `(d^(2))/(8D)`
D. `(d^(2))/(12D)`

Answer

B

Explanation

Distance of the 5th dark fringe from the centre `=(9)/(2)`X
`therefore` It is opposite to one slit.
`therefore 9/2 X=d/2' "therefore 9(lamdaD)/(d)=d`
`therefore lamda=(d^(2))/(9D)`