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Photon theory of light is considered one the most difficult concept.
28 Questions around this concept.
A charged oil drop is suspended in a uniform field of 3 x 104 V/m so that it neither falls nor rises. The charge on the drop will be (take the mass of the charge = 9.9 × 10-15 kg and g = 10 m/s2)
Microwave oven acts on the principle of :
If a source of power 4 kW produces 1020 photons/second, the radiation belongs to a part of the spectrum called
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Photon of frequency has a momentum associated with it. If is the velocity of light, the momentum is
Photon theory of light -
According to Eienstein's quantum theory light propagates in the bundles (packets or quanta) of energy, each bundle being called a photon and possessing energy. The energy of one quantum is given by, hν , where h is the Planck's constant and ν is the frequency.
where c = Speed of light, h = Plank's constant =
= Frequency in Hz , = Wavelength of light.
(In the form of eV)
Properties of Photon
After energy now let us discuss the mass of the photon.
Mass of photon :
You will study in the theory of relativity that the rest mass of any body is given by -
As the velocity of photon is same as speed of light, so from the above equation we can write that - . But it's effective mass is given as -
It is also called as kinetic mass of the photon.
Momentum of the photon -
As the momentum of any body is =
Here the velocity = c, i.e., speed of light. So, we can write that -
Note -
1. In a photon particle collision, total energy and total momentum will be conserved but the number of photons may be changed.
2. All photons of light of a particular freq. (or) wavelengths have the same energy and momentum whatever may be the intensity.
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