A light wave of wavelength `lambda_(0)` propagates from point A to point B. We introduce in its path a glass plate of refractive index n and thickness l. Then introduction of the plate alters the phase of the plate at B by an angle `phi`. If `lambda` is the wavelength of light on emerging from the plate, then

Options

A. `Delta phi = 0`
B. `Delta phi = (2 pi l)/(lambda_(0)`
C. `Delta phi = 2 pi l ((1)/(lambda) - (1)/(lambda_(0)))`
D. `Delta phi = (2 pi l)/(lambda_(0)) (n - 1)`

Answer

c.,d

Explanation

`phi_(f) = (2 pi)/(lambda_(0)) l`
`phi_(f) = (2 pi)/(lambda) l`
`Delta phi = 2 pi l ((1)/(lambda) - (1)/(lambda_(0)))`
Further, by Snell's law,
`n lambda = (1) lambda_(0) implies lambda (l_(0))/(n)`
`implies Delta phi = (2 pi l)/(lambda_(0)) (n - 1)`