10th Physics | Light: Reflection and Refraction | Light

Introduction of Light

Light is a form of energy which produces the sensation of vision in us.

NATURE OF LIGHT

The study of light is called optics and is classified in the following ways :

PARTICLE THEORY OF LIGHT

According to the particle theory of light, light is composed of particles which travel in a straight line at a very high speed. The elementary particle that defines light is known as photon.

The phenomenon of reflection and refraction of light and casting of shadow of objects by light can only be explained by particle theory of light.

WAVE THEORY OF LIGHT

According to wave theory, light consists of electromagnetic waves. The light waves travel with a very high speed of 3 × 108 m/s in vacuum.

The wavelength of visible light waves lies between 4 × 10–7 m to 8 × 10–7 m.

The phenomenon of diffraction (bending of light around the corners of tiny objects) interference and polarization of light can only be explained if the light is considered to be of wave nature.

MODERN QUANTUM THEORY OF LIGHT

Quantum theory of light reconciles the particle properties of light and its wave properties.

According to this theory light has a dual nature: light exhibits the properties of both wave and particle. Light is emitted or absorbed as a particle and light propagates as a wave.

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