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Theories Of

LIGHT

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Theories Of LIGHT

Presented By_

Md. Abu Noman JumaedID:- 142-15-3472

Md. Ghulam MartuzaID:- 142-15-3691

Md. Hannan TalukderID:- 142-15-3715

Samiul Islam Md. AkhteruzzamanID:- 142-15-3713

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A long time ago . . . Aristotle (384 - 322 B.C.), an ancient Greek thinker, thought

that we saw the world by sending “something” out of our eye and that reflected from the object.

In Plato’s time (427 – 347 B.C.), the reflection of light from smooth surfaces was known. He was also a Greek.

The ancient Greeks (about 200 A.D.) also first observed the refraction of light which occurs at the boundary of two transparent media of different refractive indices.

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In the 17th century, some properties of light were well known already. For example:

Light has different colors.

Light can travel through a vacuum.

Light can be reflected and refracted, these processes are described by the Laws of Reflection and Laws of Refraction.

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Theories of Light :-

The theories listed below are only a few of the numerous theories created by many different scientists to explain the nature of light. These four theories are the major and most known theories of the vast collection of theories about the nature of light.

The Corpuscular Theory The Wave Theory The Electromagnetic Theory The Quantum Theory

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Created in the seventeenth century by Sir Isaac Newton.

The Corpuscular Theory

Thought that light traveling from air into water will increase the speed, while light entering water will decrease the speed

States that light emitted by luminous

objects consist of tiny particles of matter

called corpuscles. When corpuscles hit a

surface, each particle is reflected.

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Why does light travel in straight lines?

A ball thrown into space follows a curved path because of gravity.

Yet if the ball is thrown with greater and greater speed, its path curves less and less.

Thus, billions of tiny light particles of extremely low mass travelling at enormous speeds will have paths which are essentially straight lines.

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The Wave Theory

Discovered by Christian Huygens, a Dutch scientist, also in the seventeenth century

Furthermore, he disagreed with Newton and said that light traveling from air to water will decrease the speed, and vice versa. Huygens was proved later to be correct.

States that light is emitted in a series

of waves that spread out from a light source in

all directions. These waves are not affected by

gravity.

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The Wave Theory

100 years later, Englishman Thomas Young completely disproved the corpuscular theory by showing that

light waves can interfere with each

other.

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The Electromagnetic Theory

Discovered in the nineteenth century

by James Maxwell.

Light waves posses electrical and magnetic properties and can travel though a vacuum.

Light waves are a part of a larger family of

electromagnetic waves and make up the

electromagnetic spectrum.

Proposed that light waves do not

require a medium for transmission.

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The Quantum Theory

Discovered by Max Planck,

German scientist in 1900

Merged the subjects of the Corpuscular, Wave, and Electromagnetic Theories together

Stated that light waves travel as separate packets of energy called quanta or photons.

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Thank You. . .!