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Let us now see what happens when a ray of light is incident on the boundary separating the two media having different densities.
A part of the light gets reflected and rest of the light changes its direction as it enters the second medium.
The diagram shows how the light gets refracted when it is travelling from one optical medium to another.
Like reflection, refraction of light takes place according to certain laws. Before we state these laws let us get familiar with certain terms which are commonly used to explain the phenomenon of refraction.
Incident Ray (IO)
The ray of light striking the surface of separation of the media through which it is travelling is known as the incident ray.
Point of Incidence
(O) The point at which the incident ray strikes the surface of separation of the two media is called the point of incidence.
Normal (N)
The perpendicular drawn to the surface of separation at the point of incidence is called the normal.
Refracted Ray (OR)
The ray of light which travels into the second medium, when the incident ray strikes the surface of separation between the media 1 and 2, is called the refracted ray.
Angle of Incidence (i)
The angle which the incident ray makes with the normal at the point of incidence, is called angle of incidence.
Angle of Refraction (r)
The angle which the refracted ray makes with the normal at the point of incidence, is called angle of refraction.
Cause of Refraction
A ray of light refracts or deviates from its original path as it passes from one optical medium to another because the speed of light changes.
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