Gamma rays have the shortest wavelength of the electromagnetic spectrum, followed by X-rays and ultraviolet rays. Slightly longer wavelengths of electromagnetic radiation, between 4000 and 7000 angstroms in length, are visible to human eyes. Infrared rays have wavelengths over 7000 angstroms, while microwave waves are even longer. Radio waves, with the longest wavelengths of all, are at least 1 billion angstroms long, equal to about 4 inches in length.
Frequency and wavelength are inversely proportional to each other. For example, radio waves have very long wavelengths but very low frequency. By contrast, gamma rays have very short wavelengths but very high frequency. The differences in the wavelengths and frequencies of the different types of waves are important to the properties of the energy. For example, astronomers use infrared light to see through clouds when visible light does not work. Some animals, such as bees and birds of prey, can see ultraviolet light, which helps them to see things that are invisible to humans.
The properties of some types of waves vary within their portion of the spectrum. For example, ultraviolet radiation at the low end of the frequency range is usually harmless, but ultraviolet radiation at the very high end of the frequency range is destructive to living creatures.