The momentum of a photon is intricately linked with its energy. Similarly, the energy of a photon is proportional to its frequency; the momentum of a photon is linked with its wavelength. The momentum of a photon can be calculated using the formula: p = h/λ
Momentum of Photon Formula
Einstein described the momentum (p) of a photon with the given formula: p = h/λ
p = the momentum of the photon (measured in Kg.m/s)
h = the Planck’s constant has a value of 6.63×10−34 J ⋅ s
λ = the wavelength of the wave bearing the photon in meters.
Note: Seeing that the value of the “h” is low the momentum of the photon is insignificant in most cases. This is validated by the fact that the mirror doesn’t draw back when the photons bounce off it.
Importance of Momentum of Photon Formula
In quantum mechanics, Photon is a crucial particle. Light and other such rays are composed of photons. Albert Einstein was the first scientist to bring into light this concept. It announced a new era in the world of physics.
Solved Example Using Momentum of Photon Formula
Calculate the momentum of a photon of light in a beam of light having a wavelength of 4x10−7 meters. Apply the Momentum of Photon Formula to find the answer.
We already know that the momentum of the photon formula is: p=h/λ
Substituting the values, p = 6.63×10−34 J ⋅ s 4x10−7
= 1.6575×10−27 kg⋅ m/s