Question

A lens (`mu=1.5`) is coated with a thin film of refractive index `1.2` order to reduce the reflected form its surface at`lambda=4800Å`.Find the maximum thickness of the film which will minimized the intensity of the reflected light .(Assume near normal incidence)

Answer 1

Correct Answer - `10^(-7)m`
Path difference =`(lambda)/(2)`
`2mu_(1)t=(lambda)/(2)`
`t=(lambda)/(4mu_(1))rArr t=4800Å/(4xx1.2)`
`t=1000Å implies t=10^(-7)m`