## Main Features of Photons:

Electromagnetic radiations (like light waves, radio waves etc.) carry energy in packets or bundles known as Photons or Quanta. The main features of Photons are as under-

1:- Photons travel in a straight line.

2:- The energy of the Photon is given by-

E = hν = hc/λ |

Where ‘h’ is Planck’s constant and its value is 6.62 x 10^{-34} Js, ‘ν’ is the frequency of Photon, ‘λ’ is the wavelength of Photon and ‘C’ is the velocity of light.

3:- All Photons travel in space with the same speed (equal to the speed of light).

4:- Photons are electrically neutral.

5:- The energy of the Photon is usually expressed in electron-volt where-

1ev = 1.6 x 10^{-19} J |

6:- Photons are not deflected by electric and magnetic fields.

7:- The momentum of the Photon is given by-

mc = h/λ |

8:- The mass of the Photon is given by-

m = h/cλ |

9:- From the theory of relativity-

m = m_{0}/√[1 – (ν’^{2}/c^{2})] |

Where m_{0} is the rest mass of the particle.

∴ m_{0} = m √[1 – (ν’^{2}/c^{2})]In case of Photon, ν’ ≈ C ⇒ m _{0} = 0 |

Hence Photon has zero rest mass. Hence, Photon cannot exist at rest.

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