How did albert Einstein prove that light travels in the form of photons?

Answer 1

This query too is an interesting one to roam about.

Have we ever seen two waves traversing on the calm surface of water give out collision among themselves? No and never! Is it not?

That is why scientists used these terms as first and foremost, while they start explaining about the superposition of waves.

"Each and every wave would travel in the medium as if the other waves were absent."

If this is the fate of the waves, then how is it possible for waves such as light when falling on a substance to kick off electrons to come out of the surface. This phenomenon is known as photo electric emission.

First light energy was assumed to be made of corpuscles by Sir Issac Newton. But his theology failed as he declared a wrong idea that the speed of light is more in denser medium. But, by practical experiments done by Foucault and others, that was disproved. Hence wave theology was proposed by Christian Huygens. Sticking on to this wave aspect, James Clark Maxwell proposed electromagnetic wave theory stating that light is not a mechanical wave as sound wave. Light can pass through even through non material medium such as free space, collocqualy saying, vacuum. Hence a wave is able to kick off material like electrons right from the atom. This will be possible only when light is in the form of some particle like which has at least momentum to kick. Hence photon concept was introduced by Einstein. But this quantum concept was already brought to light by Max Planck. That was applied to light energy by Einstein and he named those quanta of light as photons. Photon's rest mass is zero but it has momentum, which is measured right from its wavelength. P = h/ lambda. h is Planck's constant and its value is found to be 6.626 x 10 -34 Js.

Answer 2

Einstein's work on the photoelectric effect in 1905 showed that light behaves as discrete packets of energy called photons, not just as waves. He explained how light can eject electrons from a metal surface only when the light delivers a certain amount of energy, which is quantized in individual photon particles. This helped establish the dual nature of light as both a wave and a particle.