Question

A ray of light travelling through air falls on the surface of a glass slab and emerges out of it parallel to the
incident ray. The angle of incidence i, angle of refraction in glass r and angle of emergence is e. Find the ratio of sin i/sin e and refraction index of glass in terms of e and

Answer 1

Answer:

Explanation:

Consider two parallel rays A and B coming through the medium 1 (say air) to the medium 2 (say water). Upon arrival at the interface L between the two media (air and water), they continue their parallel course in the directions U and V respectively.

Let us assume that at time t=0, light ray A arrives at the interface L at point C, while ray B is still shy of the surface by a distance PD. B travels at the speed v1=cn1 and arrives at D in t seconds. During this time interval, ray A continues its journey through the medium 2 at a speed v2=cn2 and reaches the point Q.

We can formulate the rest, geometrically (looking at the parallel lines) from the figure. Let x denote the distance between C and D.

xsin(θi)xsin(θr)======PDv1tcn1tCQv2tcn2t

Thus,

n1sin(θi)n2sin(θr)==cxtcxt

Re arranging this will take us to the Snell's law as we know.

n2n1=sin(θi)sin(θr)