LIGHT THEORIES-CORPUSCULAR,WAVE,ELECTROMAGNETIC,QUANTUM,PHTOELECTRIC

                                LIGHT

Different Theories

Corpuscular theory

By Isaac Newton

Light emitted from a source is  the flow of very minute, elastic, invisible , spherical shaped corpuscles. This theory can explain Rectilinear propagation of light,Reflection and Refraction.                                                                                       Newton's fault on explanation of Refraction

Newton argued that the velocity of light increases with increase in density of medium. But Leon Foucault invented light has maximum speed in vacuum

This theory cannot explain Interference, Diffraction and color vision

Wave Theory of Light

By Christian Huygens

Light is propagated in the form of waves. Like sound wave light is also a longitudinal wave also composed of compression and Refraction

This theory can easily explain Diffraction, Reflection, Refraction

 Famous Scientist Thomas Young done a lot of experiments on Optical Phenomenon

Correction of Wave theory

By Augustin Fresnel

Gives a satisfactory explanation of Diffraction, linear propagation based on wave theory. He find out light is Transverse wave instead of longitudinal wave

 Electro magnetic Theory of Light

By James Clark Maxwell

James Clark Maxwell discovered, An electro magnetic wave can propagate as transverse wave in a suitable medium at a speed of  3*10^8 m/s.

Heinrich Hertz confirmed that light is a electromagnetic wave.

This theory cannot explain Photo Electric Effect

Photo electric effect

 light rays, Ultra violet rays, Gama rays falls on certain metal surfaces emits electrons from it. It is discovered by Heinrich Hertz

Quantum theory of light

By Max Planck

 

Radiant energy is not a continuous flow of energy. Energy emitted or absorbed from a light source is in the form of small packet of energy.This packet is called Quantum. A Quantum with definite energy is called Photon

Albert Einstein gives a satisfactory explanation for Photo electric effect based on Quantum Theory

 

         Explanation: When Photons of definite energy falls on the surface of certain metals they collide with electrons present in the atom and that electrons emitted from the surface . One photon can eject one electron.As the intensity of light increases the number of photons increases. as a result more electrons knocked out from the surface of the metal

Dual nature of Light

Light is an electromagnetic wave with particle nature and wave nature at the same time