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Light

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Overview

Light is a form of energy which produces the sensation of sight. When a light rays travels from rarer to a denser medium, it bends towards the normal. This note gives us the information about light and refraction of light.
Light

Light is a form of energy which produces the sensation of sight. The main source of heat and light energy in the earth is the sun.

Refraction of light

The bending of light as it passes from one medium to another medium is called refraction of light.

Laws of refraction of light

  • The incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane.

In the figure, the incident ray AO refracted ray OB and normal ray MN at the point of incidence O; all lie in the same plane.

  • The ratio of the sine of the angle of refraction is constant for a given pair of media. This is also called Snell’s law.

Mathematically,

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i.e = (µ) constant.

In the figure,∠ i is the angle of incidence in the air and ∠ r is the angle of refraction. In another medium glass in which the light enters. The ‘constant’ is called refractive index (R.I.) of the glass where light enters. It is denoted by µ.

The Snell’s law can be stated in the following ways:

  • When a light rays travel from rarer to a denser medium, it bends towards the normal. It means the angle of incidence is greater than the angle of refraction.
  • When the light passes from a denser to a rarer medium, it bends away from the normal. It means the angle of incidence (∠i) is smaller than the angle of refraction (∠r).
  • When the light passes along the normal i.e. at a right angle to the surface, it passes without deviation.
Things to remember
  • Light is a form of energy which produces the sensation of sight.
  • The main source of heat and light energy in the earth is sun.
  • The bending of light as it passes from one medium to another medium is called refraction of light
  • When a light rays travels from rarer to a denser medium, it bends towards the normal.
  • When the light passes along the normal i.e. at right angle to the surface, it passes without deviation
  • It includes every relationship which established among the people.
  • There can be more than one community in a society. Community smaller than society.
  • It is a network of social relationships which cannot see or touched.
  • common interests and common objectives are not necessary for society.
Videos for Light
Refraction and Snell's Law
Refraction Of Light
Snell's Law Examples 1
Questions and Answers
A light is a form of energy. A beam of light always travels in a straight line but when it passes from one medium to another, it gets bent.
The mediums of light are as follows:
  1. Rarer medium: The medium with less density in comparison to other medium is called rarer medium.
  2. Denser medium: The medium with greater density compared to other medium is called denser medium.
Eg: For air and water, air is rarer and water is denser
For water and glass, water is rarer and glass is denser.
The process of bending of light as it passes from one medium to another medium is called refraction of light.
The velocity of light in rarer medium is higher than the denser medium. Because of variation in speed of light at two media, it bends. So the change in speed of light when it passes from one medium to another medium is the main cause of refraction.
The effects of refraction are as follows: (i) A stick partly immersed in water and placed inclined to the surface, appears bent at the surface. (ii) A swimming pool appears swallower than it really is.
Quiz

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