Question

Calculate the number of photon required to generate 1 joule of energy using highest wave length of 400nm

Answer 1

Here we will use the relation

E = hν (1)

where E is the energy of the photon, h is the planck's constant and ν is the frequency of the photon. Now we also have the relation

c = νλ

where c is the speed of light, ν is the frequency and λ is the wavelength. Therefore, equation (1) becomes

E = hc / λ

Thus the energy of 1 photon in a radiation of wavelength 400 nm is

= (6.63 X 10-34 X 3 X 108) / (4 X 10-7)

= 4.972 X 10-19 J

Now the number of photons that would be required to provide an energy of 1 joule

= ( 1 / 4.972 X 10-19)

= 2.011 X 1018

Therefore 2.011 X 1018 of photons would be required to provide 1 Joule of energy.