In
physics, a
photon is an
elementary particle, the
quantum of
light and all other forms of
electromagnetic radiation, and the
force carrier for the
electromagnetic force. The effects of this
force are easily observable at both the
microscopic and
macroscopic level, because the photon has no
rest mass; this allows for
interactions at long distances. Like all elementary particles, photons are currently best explained by
quantum mechanics and exhibit
wave–particle duality, exhibiting properties of both
waves and
particles. For example, a single photon may be
refracted by a
lens or exhibit
wave interference with itself, but also act as a particle giving a definite result when its
position is measured.