Photon ([gamma])
A quantum of electromagnetic radiation. Electromagnetic radiation
shows both wave-like and particle-like properties, and a photon may
be considered to be a discrete wave packet. The energy, E,
carried by a photon is related to the
wavelength, [lambda], of its radiation by the formula
E = h*c/[lambda] = h*[nu]
where h is the Planck's constant,
c is the velocity of light, and [nu] is frequency.