This document discusses refraction of light through plane and curved surfaces as well as glass prisms. It defines refractive index as the ratio of the speed of light in one medium to the speed in another. Snell's law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant, known as the refractive index, depending on the optical densities of the two media. Total internal reflection occurs when light passes from a denser to a less dense medium and the incident angle exceeds the critical angle.

1. PHYSICS
REFRACTION OF LIGHT ON PLANE
SURFACES, CURVED SURFACES
AND GLASS PRISMS
Short revision series

2. Refractive index
 Refractive index = real depth
apparent depth
i
r
Medium 1
Medium 2

3. Laws of refraction
1. The incident ray, the reflected ray and the
normal at point of incidence all lie in the
same plane
2. SNELL’s law: The ratio of the sine of the
angle of incidence to the sine of the angle of
refraction is a constant for a given pair of
media
 the constant is known as the refractive
index
 ang = sin i (air) = velocity of light in air
 sin r (glass) velocity of light in glass

4. Eg
 If the angle of refraction is 200 , What is the
angle of incidence if the refractive index of
air to glass is 1.5?

5. solution
ang = sin i/sin r
1.5 = sin i/sin 20
sin i = 1.5sin20 = 1.36
i = sin-1 1.36

6. Refraction of light through a trangular
prism
 n = sin ½ (dm + A)
sin ½ A
 A= refracting angle of prism
 dm = minimum angle of deviation
i
r r
dm
A

7. Total internal reflection and critical
angle
 Total internal reflection occcurs when the
critical angle is exceeded for light travelling
from a dense to a less dense medium
 Critical angle is the incident angle at which
the angle of refraction is 900 when light
passses from a denser to a less dense
medium.
 ang = 1/sinC