Electromagnetic radiation is a combination of oscillating
electric and magnetic fields propagating through space and
carrying energy from one place to another. Light is a form of
electromagnetic radiation. The theoretical study of
electromagnetic radiation is called electrodynamics, a subfield
of electromagnetism. Any electric charge which accelerates
radiates electromagnetic radiation. When any wire (or other
conducting object such as an antenna) conducts alternating
current, electromagnetic radiation is propagated at the same
frequency as the electric current. Depending on the
circumstances, it may behave as waves or as particles. As a
wave, it is characterized by a velocity (the velocity of light),
wavelength, and frequency. When considered as particles, they
are known as photons, and each has an energy related to the
frequency of the wave given by Planck's relation E = hv, where E
is the energy of the photon, h is Planck's constant - 6.626 ×
10-34 J·s - and v is the frequency of the wave. Einstein later u