Polarisation and invisible radiations

Besides visible light there are other radiations on the electromagnetic scale. Infrared (IR) radiation (λ ≈ 760 nm to 1 mm) was found by Herschel in 1800 beyond the red end of the solar spectrum; every warm body emits it and we sense it as heat. Uses: remote controls, night vision and thermography, heaters, drying. Ultraviolet (UV) radiation (λ ≈ 10–400 nm) was found by Ritter in 1801 beyond the violet end; the main source is the Sun, and also special lamps. It tans the skin and in excess burns it and damages the eyes; it is used for disinfection, checking banknotes and in medicine. X-rays (λ ≈ 0.005–100 nm) were discovered by Röntgen on 8 November 1895 (the first Nobel Prize in Physics, 1901); they are produced when accelerated electrons are suddenly stopped at an anode (about 1 % of the energy becomes radiation, the rest heat, so the anode is cooled). X-rays are absorbed differently by body tissues, so images of bones can be made; they are also used in flaw detection, in studying crystal structure and in security checks. X-rays and strong UV damage living cells, so they are used only by specialists with limited doses.