Any body or object that has a temperature above absolute zero (0 Kelvin) emits infrared radiation (IR).
This type of radiation is not visible to the human eye, since its wavelengths are outside the visible spectrum (between 700 nm and 1 mm).
Infrared waves can be divided into:
- Near infrared or long wave infrared: it is the least sensitive to color and is easily absorbed by water.
- Medium or medium wave infrared: it is also insensitive to color and easily absorbed by water and many types of plastics and paints.
- Far infrared or short wave infrared: it is more penetrating than the long wave and is good for heating metals, these waves also can pass through clear materials.
It should be noted that infrared rays only cause an effect if they are absorbed. When this happens they become in thermal energy (heat).
IR light has many uses, including heating lamps in physiotherapy and medical treatments, heat sensing devices, among others.
