Energy (E) of a photon = hc/λ
Where,λ = wavelength of light = 4000 pm = 4000 x 10-12 m = 4 x 10-9 m
c = velocity of light in vacuum = 3 × 108 m/*
h = Planck’* constant = 6.626 × 10-34 Js
therefore the energy of photon (E) = 6.626 × 10-34 Js X 3 x 108 m/* / 4 x 10-9 m
= 4.965 x 10-16 J
Now 4.965 x 10-16 J is the energy of = 1 photon
Therefore 1 J will be the energy of = 1/4.965 x 10-16 J = 2.014 x 1015 photons
