In a biprism expeirment , the distance between the slit and the biprism is 20 cm and the distance between the biprism and focal and plane of the epyepiece is 80 cm. Whith the separation between two virtual images of the slit seperation between two virtual images of the slit is 0.4 cm, an interfence pattern is obtained with a light of wavelength `5500Å` .The distance between the third and eighth bands on the same side of the central bright band is

Options

A. `1.68 mm`
B. `3.68 mm`
C. `2.68mm`
D. `0.68` mm

Answer

D

Explanation

`x_(8b)-x_(3b)=8beta-3beta=5beta=5(Dlamda)/(d)`
`=(5xx1xx5.5xx10^(-7))/(4xx10^(-3))=(275xx10^(-5))/(4)`
=0.68 mm