everyday usage, we use the word light to mean only those
forms of radiation that we can see. For our purposes we
will use light to mean all of the frequencies of radiation
shown in the diagram below, known as the electromagnetic
spectrum or EMS.
EMS has been broken up into types, consisting of bands of
frequencies, as shown below, gamma rays, x-rays, etc. We
have found uses for many of these types of radiation, examples
of which are given below.
is always in motion and cannot be stored, so it is a kinetic
type of energy. You might say that light is essentially
"pure" energy, since it theoretically has no mass.
x-ray pictures of internal parts of the body. Some parts of
the body allow x-rays to pass while others, like bones, do not.
telescopes, lamps, traffic stop lights, flashlights, etc.
vision glasses, heat lamps, tanning lamps.
of objects such as airplanes, boats, people or the speeds of
communications and radio telescopes.
Light is simultaneously
a wave and a particle. The higher the frequency, the more energy
the light or electromagnetic radiation contains. The greater the
frequency, the more energy each particle, called the photon, contains.