In Young's experiment the distance between two slits is `d/3` and the distance between the screen and the slits is 3D. The number of fringes in `1/3` metre on the screen, formed by monochromatic light of wavelength `3lambda`, will be:

Options

A. `d/(9Dlamda)`
B. `d/(27Dlamda)`
C. `d/(81Dlamda)`
D. `d/(Dlamda)`

Answer

C

Explanation

`beta=(lamda.D.)/(d.)=(3lamda3D)/(d//3)=27(lamdaD)/d`
No. of fringes = `(1//3)/beta=d/(81lamdaD)`.