Newton’s Corpuscular Theory of Light

Corpuscular Theory :- This was the first noticeable theory to explain the nature of light. Newton proposed that light is made up of tiny, light and elastic particles called corpuscles which are emitted by a luminous body.

 According to Corpuscular Theory :-

• Light is made up of massless and very energetic particles called corpuscles (means very small particle).
• These corpuscles travel with a speed equal to the speed of light in all directions in straight lines and carry energy and momentum with them.
• When these corpuscles strike the retina of the eye, they produce the sensation of a vision.
• The reflection of light is analogous to the elastic collision of a ball with a wall.
• The corpuscles of different colours are of different sizes (red corpuscles larger than blue corpuscles). [This is actually a wrong prediction by Newton because the colour of light does not depend upon the size of the corpuscle but it depends upon the wavelength of light]
• Corpuscles are attracted by a transparent medium.

Failure of Corpuscular Theory

• Corpuscle theory could not explain partial reflection and refraction at the interface.
• It gave wrong prediction about the speed of light in a transparent medium.
• It gave wrong prediction about the colour of light (corpuscles of different colours are of different sizes).
• It could not explain interference (formation of bright and dark fringes) and diffraction of light (bending of light at sharp corners).