Light in certain cases may be considered as a stream of particles called "photons". Each photon has a linear momentum hλ where h is the Planck's constant and λ is the wavelength of the light. A beam of light of wavelength λ is incident on a plane mirror at an angle of incidence θ. Calculate the change in the linear momentum of a photon as the beam is reflected by the mirror.
The situation is depicted as shown in figure.