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Dynamic or kinetic mass 0f photon m = hv / c 2 = h / cλ
where c is speed of light in vacuum and λ is wavelength of radiation. Photons are electrically neutral.
A body can radiate or absorb energy in whose number multiples of a quantum hv, 2hv, 3hv …. nhv, where n is positive integer.
Photoelectric Effect
The phenomena of emission of electrons from a metal surface, when radiations of suitable frequency is incident on it, is called photoelectric effect.
Terms Related to Photoelectric Effect
( i) Work Function( φ) The minimum amount of energy required to eject one electron from a metal surface, is called its work function.
( ii) Threshold Frequency( v o) The minimum frequency of light which can eject photo electron from a metal surface is called threshold frequency of that metal.
( iii) Threshold Wavelength( λ max) The maximum wavelength rJ light which can eject photo electron from a metal surface is called threshold wavelength of that metal.
Relation between work function, threshold frequency and threshold wavelength φ = hv o = hc / λ max
Laws of Photoelectric Effect
1. For a given metal and frequency of incident light, the photo electric current( the rate of emission of photoelectrons) is directly proportional to the intensity of incident light.
2. For a given metal. there is a certain minimum frequency, called threshold frequency, below which there is no emission of photo electrons takes place.