What is meant by refraction of light? How does a ray bend as it passes from one transparent medium to another.
Refraction of light: The phenomenon of bending of light from its straight line path as it passes obliquely from one transparent medium to another is called refraction of light.
The path of the ray of light in the first medium is called incident ray.
The path of the ray of light in the second medium is called refracted ray.
The angle between the incident ray and the normal at the surface of separation is called angle of incidence (i).
The angle between the refracted ray and the normal at the surface of separation is called angle of refraction (r).
Whenever a ray of light passes from one medium another, the following three situations are possible: 
Fig.Refraction of light
(i) When a ray of light passes from an optically rarer medium to a denser medium, it bends towards the normal and angle of refraction (∠r) < angle of incidence (∠i), as shown in Fig.(a).
(ii) When a ray of light passes from an optically denser to a rarer medium, it bends away form the normal and angle of reflection(r) > (i) as shown in Fig.(b).
(iii) A ray of light travelling along the normal passes undeflected. Here ∠ i = ∠ r = 0°.
