### Refraction of Light - simulator for GCSE, IGCSE, A Level, IB, GCE O Level, GCE A Level

Refraction
When light moves from a medium to another medium, its speed and the direction changes. This is called refraction of light.

Snell's Law
When light refracts, the ratio of the sine of the angle of incidence to the ratio of the sine of the angle of refraction remains the same for any two given media.

Equation of Refraction
n1 sin i1 = n2 sin i2

E.g. 1
A ray of light goes from air to glass at an angle of 600 to the surface. If the refractive indices of air and glass are 1 and 1.5 respectively, find the angle of refraction and determine the nature of refraction.
n1 = 1 n2 = 1.5 i = 30 r = ?
1 sin 30 = 1.5 sin r
sin r = 0.5/1.5 = 1/3
r = sin-1 (1/3)
r = 19.60
The ray bends towards the normal; hence, the latter is a denser medium.

E.g. 2
A ray of light goes from water to air at an angle of 500 to the surface. If the refractive indices of air and water are 1 and 1.3 respectively, find the angle of refraction and determine the nature of refraction.
n1 = 1.3 n2 = 1 i = 40 r = ?
1.3 sin 40 = 1 sin r
sin r = 1.3 sin 40
r = sin-1 (1.3 sin 40)
r = 56.90
The ray bends away from the normal; hence, the latter is a less dense medium.

E.g. 3
A ray of light goes from glass to air along the surface. If the refractive indices of air and glass are 1 and 1.5 respectively, find the angle of refraction and determine the nature of refraction.
n1 = 1 n2 = 1.5 i = 90 r = ?
1 sin 90 = 1.5 sin r
sin r = 1/ 1.5
r = sin-1 (1/1.5)
r = 41.80
The ray bends towards the normal; hence, the latter is a less dense medium; this is a special angle, called the critical angle for glass/air.

You can practise refraction interactively here: