Photons

A Photon is a discrete packet of electromagnetic radiation . It is the elementary exchange particle for the electromagnetic force. The Energy of a photon depends on its frequency and is given by the equation:

$E=hf$

where f is the frequency of the electromagnetic wave and h is Planck's constant and has the numerical value of $6.626\times 10^{-34}$Js (Joules times second) or $4.135\times 10^{-15}$eV s (electron volts times second).