Just beyond the wavelengths of visible light, or the seven colors of the spectrum, is Infrared and Ultraviolet light. These as-well as others make up the electromagnetic spectrum.
Electromagnetic Spectrum
Gamma-Rays, X-Rays, Ultraviolet, Visible Light, Infrared, Microwaves and Radio Waves.
Infrared Light
Infrared (IR) light or radiation is not detectable to the human eye, and is emitted by all objects in the known universe. The biggest emitter of infrared light/radiation is stars, like our own Sun.
We cannot see infrared light because it’s just out of range of the visible spectrum, similar to ultra-violet light, but on the opposite side of the electromagnetic spectrum. The wavelength of infrared is beyond the visible color red, with an estimated wavelength of 750+ nm.
Infrared was detected by William Herschel, a British astronomer. He was actually running an experiment while he was trying to detect temperature differences in the different wavelengths/colors of the visible spectrum. He successfully detected differences in temperatures from short to long wavelengths, or from colors blue to red. As he moved beyond the 700 nm range of red in the visible spectrum, he discovered infrared.
Infrared wavelengths also vary greatly. At the shorter end of the scale, infrared produces virtually no heat, often used in the remote controls on your TV, DVD players and other devices. At the other end of the infrared scale, it gets closer to microwave frequencies, which generate a great amount of heat. This is the radiation that fire and stars emit.
Heat vision and night vision cameras, telescopes and goggles use infrared. Everything is known to emit infrared radiation. These devices have special sensors that detect infrared light, enabling people to see in the dark, or to search for things that would be undetectable otherwise.
Ultraviolet Light
Ultraviolet light is on the opposite side of visible light in the electromagnetic spectrum, with a wavelength of around 380nm. Ultraviolet light is responsible for sun tans, and if the skin is exposed to too much UV light, sun burns will be the result. UV light is invisible to the human eyes. However, too much of it can damage our skin, eyes, and bodily tissue in general.
Ultraviolet light is produced by stars, in our case the Sun. This is a natural form of UV light. It can also be recreated by special bulbs or lamps found in tanning booths. Black lights also produce ultra violet light.
Fluorescence
There are many things, natural and unnatural, that can absorb Ultra Violet light. When UV light is absorbed by something that has fluorescent properties, some of that light is emitted back out as wavelengths along the visible spectrum, making that object or material appear brighter. This is why fluorescence is used for high visibility clothing and road signs.
Reference
https://www.livescience.com/50260-infrared-radiation.htmlon.html
