Electromagnetic radiation/Bands in the spectrum

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Electromagnetic radiation: 4. Bands in the spectrum

The electromagnetic spectrum is divided into several bands. These definitions are generally informal and vague, and the bands may overlap. There seems to be a gap between the ultra-violet and X-ray bands. Sometimes, the choice of band depends on how the radiation is generated. For example, radiation from radioactive decay is always referred to as gamma rays, even if its photon energy would class it as X-rays.

The main bands used, in order of decreasing wavelength (hence increasing frequency and photon energy) are:

  • Radio
  • Microwaves
  • Infra-Red
  • Visible light
  • Ultra-violet
  • X-rays
  • Gamma rays

A convenient mnemonic for remembering these is "Rabbits Mate In Very Unusual eXpensive Gardens".

As noted later, microwaves have only been regarded as a separate band in fairly recent years.

There are many bands within these, which are even vaguer and more prone to overlap. Each band is discussed in more detail later. The limits given are rough, so exact consistency between wavelength, frequency and photon energy cannot be expected.