X-ray photons have energies in the range 100 eV to 100,000 eV (or 100 keV). Ultraviolet radiation falls in the range from a few electron volts to about 100 eV. Instead of using wavelengths, astronomers that study these portions of the EM spectrum usually refer to these photons by their energies, measured in electron volts (eV). The wavelengths of ultraviolet, X-ray, and gamma-ray regions of the EM spectrum are very small. (This range is just a tiny part of the entire EM spectrum, so the light our eyes can see is just a little fraction of all the EM radiation around us.) Using nanometers, violet, blue, green, yellow, orange, and red light have wavelengths between 400 and 700 nanometers. Optical astronomers use both angstroms (0.00000001 cm, or 10 -8 cm) and nanometers (0.0000001 cm, or 10 -7 cm). Infrared astronomers use microns (millionths of a meter) for wavelengths, so their part of the EM spectrum falls in the range of 1 to 100 microns. Infrared and optical astronomers generally use wavelength. The radio is a very broad part of the EM spectrum. Most of the radio part of the EM spectrum falls in the range from about 1 cm to 1 km, which is 30 gigahertz (GHz) to 300 kilohertz (kHz) in frequencies. It is much easier to say or write "two kilometers" than "two thousand meters." Generally, scientists use whatever units are easiest for the type of EM radiation they work with.Īstronomers who study radio waves tend to use wavelengths or frequencies. The short answer is that scientists don't like to use numbers any bigger or smaller than they have to. But why have three ways of describing things, each with a different set of physical units?Ĭomparison of wavelength, frequency and energy for the electromagnetic spectrum. Each of these three quantities for describing EM radiation are related to each other in a precise mathematical way. Frequency is measured in cycles per second, or Hertz. Radio waves have photons with low energies, microwave photons have a little more energy than radio waves, infrared photons have still more, then visible, ultraviolet, X-rays, and, the most energetic of all, gamma-rays.Įlectromagnetic radiation can be expressed in terms of energy, wavelength, or frequency. The different types of radiation are defined by the the amount of energy found in the photons. Each photon contains a certain amount of energy. Radio waves, gamma-rays, visible light, and all the other parts of the electromagnetic spectrum are electromagnetic radiation.Įlectromagnetic radiation can be described in terms of a stream of mass-less particles, called photons, each traveling in a wave-like pattern at the speed of light. The biggest gamma-ray generator of all is the Universe.Īre radio waves completely different physical objects than gamma-rays? They are produced in different processes and are detected in different ways, but they are not fundamentally different.
Gamma ray: Doctors use gamma-ray imaging to see inside your body. Hot gases in the Universe also emit X-rays. X-ray: A dentist uses X-rays to image your teeth, and airport security uses them to see through your bag. "Hot" objects in space emit UV radiation as well. Ultraviolet: Ultraviolet radiation is emitted by the Sun and are the reason skin tans and burns. Fireflies, light bulbs, and stars all emit visible light. In space, infrared light helps us map the dust between stars. Infrared: Night vision goggles pick up the infrared light emitted by our skin and objects with heat. Microwave: Microwave radiation will cook your popcorn in just a few minutes, but is also used by astronomers to learn about the structure of nearby galaxies. Radio waves are also emitted by stars and gases in space. Radio: Your radio captures radio waves emitted by radio stations, bringing your favorite tunes.
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