Question

In YDSE, the central bright fringe produced by light of wavelength `5600 Å` shifts to the position of `5th` bright fringe when a thin transparent film of refractive index `1.28` is introduced in the path of light from one of the two slits. Find the thickness of the film.

Answer 1

Correct Answer - `10^(-5)m`
Here, `lambda = 5600 Å = 5600 xx 10^(-10)m`
`mu = 1.28, t = ?`
Shift, `x = (5 lambda D)/(d)`
As `x = (mu - 1)t xx (D)/(d) = (5 lambda D)/(d)`
`:. t = (5 lambda)/(mu - 1) = (5 xx 5600 xx 10^(-10))/((1.28 - 1)) = 10^(-5)m`