12.4 REFRACTION OF LIGHT
If we dip one end of a pencil or some other object into water at an angle to the surface, the submerged part looks bent as shown in Fig.12.7. Its image is displaced because the light coming from the underwater portion of the object changes direction as it leaves the water. This bending of light as it passes from one transparent medium into another is called refraction.
Refraction of light can be explained with the help of Fig.12.8. A ray of light IO travelling from air falls on the surface of a glass block. At the air- glass interface, the ray of light IO changes direction and bends towards the normal and travels along the path OR inside the glass block. The rays IO and OR are called the incident ray and the refracted ray respectively. The angle 'i' made by the incident ray with the normal is called angle of incidence. The angle 'r' made by the refracted ray with the normal is called angle of refraction. When refracted ray leaves the glass, it bends away from the normal and travels along a path ME. Thus
The process of bending of light as it passes from air into glass and vice versa is called refraction of light.