1)      Radiation is the energy emitted by matter in the form of electromagnetic waves (or photons) as a result of the changes in the electronic configurations of the atoms or molecules.

a)      Does not require the presence of an intervening medium.

b)      Fastest (at the speed of light)

c)      No attenuation in a vacuum

d)      Volumetric phenomenon, but considered to be a surface phenomenon for solids that are opaque

e)      Stefan–Boltzmann law

Where σ = 5.67×10^-8 W/m²K⁴ is called Stefan–Boltzmann constant.