Infrared radiation is the one with a frequency lower than the visible light and higher than the radio waves. We are therefore talking about a wavelength between 700nm and 1mm (infrared band). The term “infrared” means under (infra) red, which is the visible color with the lowest frequency of visible light.
Infrared is that electromagnetic frequency associated with heat, this is because every object with a temperature above absolute zero (basically any object) emits infrared waves in a natural way. Obviously, the higher the temperature of the object, the closer the wavelength is to visible light, until the object becomes incandescent.
There are different types of infrared depending on the wavelength detected:
- near (NIR) 0,75 µm -1,4 µm
- short wave (SWIR) 1,4 µm – 3 µm
- medium wave (MWIR) 3 µm – 8 µm
- long wave (LWIR) 8 µm – 15 µm
- far (FIR) 15 µm – 1000 µm
Near and short and medium wave infrared rays penetrate organic tissues and can cause damage. The greater the wavelength, the lower the depth of penetration into the tissues.
- Near and short wave: this is the radiation with the highest penetration depth and can affect the retina and adipose tissue.
- Medium wave: does not affect the retina and only penetrates the blood vessels, barely touching the adipose tissue.
- Long and far wave: it does not go beyond the superficial layer of the skin and cornea.