What is photon in physics? – All Secrets Revealed

Dear Reader If You want to read about What are photon in physics ? In this article i am going to uncovered all secrets of Photon.

Photons are small subatomic particles that have zero mass, unit spin and these belong to a category of bosons. This subatomics which carries the energy during electromagnetic radiation or EM radiation. So that’s why they are also known as packets of energy. Photon carries energy that cannot be divided.

What is a photon in physics ?

Momentum of a photon:

Photons are having zero rest mass. But still, they are having non-zero momentum. This is because photons are moving with the speed of light. Due to this, its momentum is directly proportional to the energy of the photon, and inversely proportional to the wavelength of the photon.

The momentum of a photon can be determined from the wavelength, energy, the frequency of particle.

The momentum of photon formula:   

Formula for Momentum of photons What is a photon in physics

The formula for Momentum of Photons

Properties of photons

Property Description
Energy E = hν
Mass When photons is at rest = zero.

When photons is in motion = e/c2

Speed of photons Speed of light ( 3 x 108 m/s)
Stable/ unstable These are stable particles
Charge They do not have charge.
Interaction with other particles After interaction they are showing 1.compton effect

2. Photoelectric effect

Conservation of energy and momentum During collision, Energy and momentum both are conserved.
Effect of Electric field and Magnetic field. They are not affected by electric field and magnetic field because they are uncharged particles.

Spin of photon

Having unit spin. (Spin 1)


What is photoelectric effect?

It is a phenomenon in which a photon of energy strike the metal surface The electrons from the metal surface eject out from it. This phenomenon is known as photoelectric effect. Ejected Electrons are known as photoelectrons. We can easily explain Photo electric effect By the Particle nature of Light.

 Conditions for the Photoelectric Effect:

  •  Photons Must have Sufficient energy to strike the material’s surface.
  •  Material must have a work function.
  •  Energy of photon must be greater than or equal to the work function for electron ejection.
  •  Frequency of incident light determines photon energy.
  •  Intensity affects photon count, not energy.
  •  Kinetic energy of emitted electrons depends on energy difference.
  •  Emission of electrons independent of intensity once the threshold is met.

State Photoelectric Effect

The photoelectric effect is the phenomenon where light (photons) can cause electrons to be emitted from a material’s surface.

Principle of Photoelectric Effect

It is based on the principle that When the light of sufficient energy fall on a metal surface, it ejects a number of Electrons from the Metal surface. The number of Electrons coming out from the metal surface depends on the frequency of the incident light. The intensity of light affects the number of electrons ejected, but not their energy.

What is a photon in physics
                                              Emission and Absorption of Photons

The phenomenon of Photoelectric Effect was first explained by:

The phenomenon of Photoelectric electric fact is first explained by Albert Einstein For the explanation of the photoelectric effect, he got a Nobel Prize in 1921.


1.Why is the momentum of a photon zero?     

Ans: No, photon carries some momentum because of the energy carries by them. We can determined the momentum of a photon using p = h/λ or E/c.

2.Is photon a particle of zero momentum?

Ans: No photon of a particle Have zero momentum. The momentum of the photon can be find out with formula p = E/c.

 3.How a photon is created?

Whenever the electrons are going from the Excited state (Higher energy state) to the Ground state (lower energy state), Electrons released the energy in the form of photons.

4.Why do photons have momentum but no mass?

In the classical concept, the Particles moving with small velocity (non-relativistic velocity) if have zero mass then it will have zero momentum. But Those particle are moving with Speed of light they do not follow this concept. There momentum can be determined by of a formula of  photon using p = h/λ or E/c.

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