A parallel beam of light of wavelength `lambda` is incident normally on a single slit of width d. Diffraction bands are obtained on a screen placed at a distance D from the slit. The second dark band from the central bright band will be at a distance given by ....

Options

A. `(2lambdaD)/(d)`
B. `lambda dD`
C. `(lambdaD)/(2d)`
D. `(2lambdad)/(D)`

Answer

A

Explanation

For diffraction condition for dark fringe `d sin theta_(n)=n lambda`
But for smaller angle `sin theta_(n)=(x_(n))/(D)`
`:. In (dx_(n))/(D)=n lambda, n=2`
`:.x_(2)=(2lambdaD)/(d)`