Question

A parallel beam of monochromatic light is incident on a glass slab at a angle of incidence 60° Find
the ratio of width of the bean in the glass so that in air if the refractive index of glass is 1.5.
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Answer 1

• The ratio of the width of the bean in the glass to that in air is 1.633:1.

Given-

Angle of incidence on the glass slab is (i) = 60⁰.

Refractive index of the glass is (μg) = 1.5

Let take Width of beam in glass slab and width of beam in air is dg and da respectively.

So we have to find the ratio of dg/da

We know that μg = sin i/ sin r -------(i)

And dg/da = cos r / cos i --------(ii)

From the (i) equation

1.5 = sin 60 / sinr

sin r = 35⁰ 16'

Now, dg/da = cos r / cos i

= cos 35⁰ 16'/ cos 60 = 0.8164/ 0.5 = 1.633

So the ratio of width of the beams is 1.633 : 1.

Regards