A laser beam is incident on a plate of glass of thickness 3

A laser beam is incident on a plate of glass of thickness 3 cm. The glass has an index of refraction of 1.5 and the angle of incidence is 40^o. The top and bottom surfaces of glass are parallel and both produce reflected beams of nearly the same intensity. What is the perpendicular distance d between the two adjacent reflected beams?

Solution

Fron snells law

theta = sin^-1 [sin 40 / 1.5] =  sin^-1 [0.643 / 1.5]

= 25.38 deg

x = 2d * tan theta * cos theta

= 2.18 cm