Question

Let the light ways moving from a material to another material. There are 2 scenarios:

- The ray is moving from water to glass. The intensity of the refracted rays is 98.92 % and the intensity of the reflected rays is 1.08%.

- The ray is moving from air to glass. The intensity of the refracted rays is 90.87% and the intensity of the reflected rays is 9.13%.

The index of diffraction of air, water, and glass are 1.00, 1.33, and 1.50 respectively.

Explain these differences in the intensity between 2 scenarios.

Answer 1

When light wave moves from one material to another material then the reflected part and refracted part of light wave can be determined by using FRESNEL EQUATION.

Since when light incident at any interface making some angle with normal then reflected and refracted part depend on the angle made by incident, reflected and refracted light along with refractive index of both materials. But for normal incidence fresnel equation can be simply expressed using refractive index of both materials.

For an interface having refractive index n1 and n2 the reflected part R is expressed as -

R = | n1 - n2 / n1 +n2 |^2

Where

n1 = refractive index of first medium in which light is incident

n2 = refractive index of other medium

And transmitted part or refracted part T = 1 - R

In first scenario two medium are water and glass and in second scenario medium are air and glass.

So here we can conclude that intensity difference between there two scenarios is due to the different refractive index of medium.