Electromagnetic or infrared radiation occupies the spectral region between the electromagnetic wave that the human eye sees, its red end and microwave or microwave radiation. A large difference in the optical properties of substances is observed between the perception in infrared and visible radiation. For example, for short-wave infrared radiation, water a few centimeters thick is opaque.
About 50% of solar radiation falls on this particular type. It is an integral part of gas discharge and incandescent lamps, and also some lasers are capable of emitting infrared radiation. To register it, photoelectric and thermal receivers or special photo materials are used.
The infrared range has three components: shortwave, mediumwave and longwave. The long wavelength region is divided into sublimated or terahertz radiation.
Human skin perceives infrared radiation from heated objects as a thermal sensation, therefore it is also called "thermal". The wavelength emitted by heat depends on the heating temperature. If the temperature is high, the wavelength will be short, and the intensity of its radiation is higher. Excited ions and atoms emit infrared radiation. In this range at relatively low temperatures lies the electromagnetic spectrum of the radiation of a completely black body.
Astronomer W. Herschel discovered electromagnetic radiation in 1800, after which infrared radiation was studied in detail. Herschel determined its properties using thermometers. As a result of the experiments, it was proved that the temperature acts differently on different parts of the visible spectrum. Herschel determined the following: the maximum heat that lies outside the saturated red color is also possible beyond its apparent refraction.
Modern laboratory sources of infrared radiation are based on molecular solid-state gas lasers. In them the frequency of radiation is regulated and fixed.
To register thermal radiation, special photographic plates are used. The photoresistor and photoelectric detector have a much wider sensitivity range.
Unusual abilities have infrared radiation. Its properties are such that it can be applied in various fields:
- medicine - in physiotherapy;
- sterilization of food for disinfection;
- remote control - in television remotes, automatic and security systems, some models of mobile phones;
- painting - the energy expended and the speed is much less than with the convection method;
- as an anti-corrosion agent;
- food industry - electromagnetic waves of a certain range have a thermal and biological effect on the product, which helps to accelerate biochemical transformations in biopolymers;
- agricultural industry;
- heating of rooms of streets and houses, for the main and additional heating;
- checking money for authenticity, etc.
Infrared radiation can be harmful to human eyes. In places where there is high heat, infrared radiation can be dangerous for the eyes even when it is not yet accompanied by a visible light source. In these cases it is necessary to use special protective glasses.
In other cases, infrared radiation can not cause harm to humans. It is absolutely safe and has nothing like ultraviolet or x-ray radiation.
The infrared radiation used in cooking makes the food very tasty, since all the minerals and vitamins are preserved, while it has nothing to do with the microwave.
In general, we can say that there are practically no areas where infrared radiation is not used today.