In a Fresnel's biprims experiment fringes widht `0.05` mm are observed on a screen at a distance of `1.5` m from the source. When a convex lens is placed between the source and the screen, are `0.04` mm and `0.1` mm resepectively. The wavelenght of light used is s

Options

A. `6.67 nm`
B. `0.6667 nm`
C. `667 nm`
D. `667Å`

Answer

B

Explanation

`d=sqrt(d_(1)d_(2)) =sqrt(0.04 xx0.01)=0.02 mm`
`lambda=(d)/(D) beta= (0.02xx10^(-3)xx0.05xx10^(-3))/(1.5)`
`=0.6667cm`