SS2 Third Term Physics Lesson Note – Refraction of Light Waves

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WEEK 5:

TOPIC: REFRACTION OF LIGHT WAVES

CONTENTS

1. Refraction of light through rectangular glass block and triangular glass prism
2. Laws of refraction
3. Critical angle and total internal reflection of light
4. Sun’ s energy and the radiation to the earth
5. Refraction of light through converging and diverging lenses
6. Dispersion of white light and colour mixing.

Sub topic 1: Refraction of light through a rectangular glass block and a triangular glass prism.

• Refraction through a rectangular glass prism

Refraction is a change in direction of light rays as the rays travel from one medium to another media of different density. Refraction takes place when light travels from air to glass or from air to water.

OA is the incident ray, OB is the refracted ray. Angle of incidence ( i ) is the angle the ray makes with the normal ON in air. Angle of refraction OB is the angle the refracted ray OB makes with the normal ON in the second medium.

The refractive index of glass with respect to air _an_g is given as

_an_g = ^{sin i}/_{sin r}

Refractive index in terms of wavelength is given as

Refractive index   n = wavelength of light in medium 1/its wavelength in medium 2     =    λ₁/λ₂

Refraction of light can be used to explain a number of phenomena such as mirage, apparent depth of a swimming pool, bending of a straight object e.g metre rule when immersed partially

Mathematically, real depth, apparent depth and refractive index ‘n’ are related by the equation

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