A double slit experiment is performed with light of wavelength `500nm`. A thin film of thickness `2mum` and refractive index `1.5` is introduced in the path of the upper beam. The location of the central maximum will

Options

A. remains unshifted
B. shift downward by nearly two fringes
C. shift upwards by nearly two fringes
D. shift downward by 10 fringes

Answer

C

Explanation

`lamda=500nm,t=2mum,mu=1.5,N=?`
`N=((mu-1)t)/(lamda)`
`=((1.5-1)xx2xx10^(-6))/(5xx10^(-7))`
N=2 shifts upward