3 Particle Nature of Light The Photon

Particle Nature of Light The Photon

• In interaction of radiation with matter, radiation behaves as if it is made up of particles called photons.
• Each photon has energy E (= hν), momentum p (= hν/c), and speed c, which is the speed of light.
• All photons of light of a particular frequency ν, or wavelength λ, have the same energy E (=hν = hc/λ) and momentum p (= hν/c), independent of the intensity of radiation. By increasing the intensity of light of given wavelength, there is only an increase in the number of photons per second crossing a given area, with each photon having the same energy.
• Photons are electrically neutral and are not deflected by electric and magnetic fields.
• In a photon particle collision, the total energy and total momentum are conserved. However, the number of photons may not be conserved in a collision. The photon may be absorbed or a new photon may be created.