REFRACTION AT PLANE SURFACES

Refraction is a phenomenon, due to which a ray of light deviates from its original path, while

travelling from one optical medium to another optical medium. The change of direction is caused

by a change in speed of light in different medium. For example, when light travels from air into

water, it slows down; causing it to continue to travel at a

different direction as a result it deviates. In the case of

homogeneous medium light travels along a straight line.

Refraction is the bending property of light as it passes from

one transparent medium to another.

When light passes from a less dense to more dense medium,

(for example passing from air into water), the light is

refracted (or bent) towards the normal as shown in [Fig. 15.1].

The bending occurs because light travels slowly in a denser

medium.

By the similar way, when light enters into less dense medium form high dense medium it speeds

up and bends away from the normal as shown in [Fig.15.1].

                                Laws of Refraction

The law of refraction is generally known as Snell's law, governs the behavior of light-rays as they

propagate across a sharp interface between two transparent media. The two laws of refraction

are,

(i) The incident ray, the normal and the refracted ray at a point of incidence all lie in the same

plane.

(ii) When a ray of light passes from rarer medium to a denser medium, the

refracted ray is closed to the normal while the ray of light passes from

denser medium to a rarer medium, the refracted ray is away from the

normal. [For any two mediums, the ratio of the sine of angle of incidence

to the angle of sine of angle refraction is constant which is called refractive

index.]


Author: Aadarsha Jha

Group: Physics Universe 

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