The electromagnetic spectrum is infinite

light

Light is an electromagnetic form of energy. It spreads in a vacuum at the speed of light in a vacuum c from almost 300,000 km / s; exact: 2.99792458 × 108 m / s. In principle, the range of light is infinite, but light usually interacts with matter, e.g. through diffraction, refraction, scattering, absorption, emission.
This means that light is able to cover large distances Energy and information to transport.

geometric optics & wave optics

The classic physical discipline that deals with light is optics. Without knowing exactly what the nature of light actually is, light is called Beam of light (geometric optics) or as Light wave (Wave optics) described purely geometrically. This relatively simple mathematical apparatus is powerful and allows a wealth of light phenomena to be described, e.g. refraction and diffraction.

Colors of light

In a narrower sense, light only means that part of the electromagnetic spectrum that is visible to humans. This begins with short wavelengths (high light energies) in the violet and goes through the colors blue, green, yellow, orange to red. More generally speaking, light comes in many colors, such as radio, thermal, optical, ultraviolet, X-ray, and gamma radiation.
These diverse forms of light make it clear how essential light is to astronomy. Classical observational astronomy was optical. Only gradually did the other observation windows of astronomy open - on the one hand, through the gradual understanding of the nature of light; on the other hand, through technological progress, which made it possible to capture light and thus create images.

Role of light

Light is of fundamental importance in many ways:

  • No brightness without light.
  • There is no warmth without light.
  • No photosynthesis without light.
  • No life without light.
  • No information without light.
  • There is no astronomy without light.

Light in the light of the great physical theories of the 20th century

According to the special theory of relativity, the speed of light in a vacuum is the absolute limit speed for information.
According to general relativity, light propagates on zero geodesics in a generally curved spacetime.
According to quantum theory, light is quantized in light particles, the photons.
According to quantum electrodynamics, a quantum field theory of light, the photons are exchange particles (gauge bosons) of the electromagnetic force.

Continue with ...

... the lexicon entry photons, which contains a lot of interesting information about light.