## Light

Subject: Science

#### 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,

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.