With the help of a ray diagram, state what is meant by refraction of light. State Snell’s law for refraction of light and also express it mathematically.
The refractive index of air with respect to glass is 2/3 and the refractive index of water with respect to air is 4/3. If the speed of light in glass is 2 x 10⁸ m/s, find the speed of light in:
a) air, b) water.

When a ray of light travels from one transparent medium to another, it bends at the surface. This happens because different media have different optical densities.
refraction of light is the phenomenon of bending of light as it travels from one medium to another is known as refraction of light.
When a ray of light moves from optically rarer medium to an optically denser medium, it bends towards the normal at the point of incidence.
Therefore, angle of incidence (i) is greater than the angle of refraction (r).

Snell's law states that, the ratio of the angle of incidence to the sine of the angle of refraction is constant.
Mathematically, it is given as,

where,  is the absolute refractive index of a medium w.r.t vacuum
c is the speed of light in vacuum
v is the speed of light in medium
a) Now,

b) We have,