Question

A central fringe of interference pattern produced by light of wavelength `6000 Å` is shifted to the position of 5th bright fringe by introducing thin film of `mu = 1.5`. Calculate thickness of the film.
A. `6xx10^(-4) mm`
B. `6xx10^(-4) m`
C. `6xx10^(-4)m`
D. 3 cm

Answer 1

Correct Answer - C
`lamda=6000A^(@),Deltabeta=5beta,mu=1.5t=?`
`Deltabeta=(beta)/(lamda)(mu-1)t`
`5beta=(beta)/(6xx10^(-7))(1.5-1)t`
`t=(30xx30)/(0.5)`
`=60xx10^(-7)m`
`=6xx10^(-4)cm`