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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 .