INTRODUCTION:

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According to quantum theory light consist of tiny discrete particles having quantized energy called photon. This theory was first introduced by Max Planck, he succesfully explained the phenomena of Black body radiations which wave theory of light could not explained. He got nobel prize for his work 1918 . Black body radiations confirms that energy absorbed or released by any body is not a continous process but a discrete process which established that light is quantized in nature. Later on Einstein and Compton succesfully explained photoelectric effect and Compton effect on the basis of quantum theory and recieved noble prize in 1921 and 1927 respectively.

So there are many questions which one has in its mind.

1. What is a photon?
2. Is it a particle?
3. how does it behaves with matter?
4. Does it carries any force? etc etc

Let us understand what actually it is, in detail. I hope it will be a useful information for many

Photons are discrete amount of electromagnetic energy. These are the carriers of electromagnetic forces.

Charge:

A photon has no charge but it can interact with all charged and the neutral particles.

Stability:

It is very stable particle have infinite life time until it interacts with other particle.

Energy:

Its energy depends upon its frequency , e.g in a visible spectrum A blue color photon has more energy as compared to a red color photon because blue color photon has more frequency as compared to a red color photon. Where as the energy of photon is inversly proportional to wave length of a photon.

Speed:

Photons have different energies but they always move with same speed in free space i.e 3 x 10⁸ m/s

Mass:

When I was discussing its stability, i wrote, it is a particle and when discussing about its energy i wrote about its frequency and wavelength, photon has dual nature it can behave as a particle as well as wave. It is a special type of particle which you cannot compare with other particles. It exist due to its own motion.
According to theory of relativity postulated by Albert Einstein
E = mc² ( m in this case is relativistic mass of photon)
According to Max Plancks
E = hν
Compairing both the equations we have
mc² = hν ................Eqn.1

m = hν/c²
As c² is very very large , m would be very very small or negligible.
E.g Let us calculate the relativistic mass of a photon in visible region having frquency 4.3x 10¹⁶ , using above formula the mass would be 3.2 x 10^-34 , this means it is 2872 times lighter than electron. That is negligible but keep in mind it is not exactly equal to zero.

Momentum:

Light contains particles called photons, perhaps they should have momentum like any other particle. In fact, light is both a wave and a particle. So, not only does it have a momentum, it also has a wavelength. Relativistic Momentum is define as relativistic mass x velocity , relativistic mass is "m" and velocity is "c , so relativistic momentum becomes "mc" which is also symbolized by "p"
Recalling Eqn (1)

mc² = hν
mc² = hc/ λ
mc = h/ λ
p = h/ λ ( de Broglie hypothesis confirmed by Davission and Germer experiment )
If calculations are made for wavelength 700 nm ( visible region ) , momentum would be 9.5 x 10 ^-28 kgm/s

I hope that my post will prove to be informative. Thankyou.

_{References:
http://study.com/academy/lesson/energy-momentum-of-a-photon-equation-calculations.html
https://en.m.wikipedia.org/wiki/Matter_wave
https://physics.stackexchange.com/questions/2229/if-photons-have-no-mass-how-can-they-have-momentum}