Energy (E) of a photon = hν
Energy (En) of ‘n’ photons = nhν
Where, λ = wavelength of light = 4000 pm = 4000 ×10–12 m c = velocity of light in vacuum = 3 × 108 m/s h = Planck’s constant = 6.626 × 10–34 Js
Substituting the values in the given expression of n:
Hence, the number of photons with a wavelength of 4000 pm and energy of 1 J are
2.012 × 1016.
