Infrared

From HvWiki

On the Electromagnetic spectrum, infrared (IR) light is off the red end of the visible spectrum. It is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. Infrared radiation spans three orders of magnitude and has wavelengths between approximately 750 nm and 1 mm. This band is split into two: the near infrared (the shorter wavelengths close to visible light) and the far infrared (the longer wavelengths associated with "heat waves").

The boundary between visible and invisible wavelengths of light is not well defined and the human eye has some sensitivity to IR light. IR light sources like lasers may be visible as a curious red colour and the normal response is to stare at the light source. Since the light can be millions or billions of times brighter than perceived it may cause permanent eye damage.

Uses of IR Radiation

Because IR has a longer wavelength than visible light it can penetrate dust and some materials better than visible light, it can be used to good effect in photographs.

Objects at around body temperature give off electromagnetic radiation in the far infrared region. Cameras that can detect far IR are then used in thermal imaging.