Einstein established the idea of photons on the basis of Planck's quantum theory. According to his idea, the light of frequency f or wavelength `lamda` is infact a stream of photons. The rest mass of each photon is zero and velocity is equal to the velocity of light `(c) = 3 xx 10^(8) m.s^(-1)`. Energy, E = hf, where h = Planck's constant `= 6.625 xx 10^(-34)J.s`. Each photon has a momentum `p = (hf)/(c)`, although its rest mass is zero. The number of photons increase when the intensity of incident light increases and vice-versa.
On the other hand, according to de Broglie any stream of moving particles may be represented by progressive waves. The wavelength of the wave (de Broglie wavelength) is `lamda = (h)/(p)`, where p is the momentum of the particle. When a particle having charge e is accelerated with a potential difference of V, the kinetic energy gained by the particle is K= eV. Thus as the applied potential difference is increased, the kinetic energy of the particle and hence the momentum increase resulting in a decrease in the de Broglie wavelength. Given, charge of electron, `e = 1.6 xx 10^(-19)C` and mass `= 9.1 xx 10^(-31) kg`.
The number of photons emitted per second by a source of light of power 30 W is `10^(20)`, the momentum of each photon (in `kg.m.s^(-1)`)

Options

A. `10^(-24)`
B. `10^(-25)`
C. `10^(-26)`
D. `10^(-37)`

Answer

D