The light that we can see (from red to violet) is only a tiny fraction of a family of transverse electromagnetic oscillations.
Beyond the red – the infrared, at longer wavelengths than visible light. All bodies above absolute zero emit infrared. If when you abandon your stolen car and run for the trees, you can’t hide. The IR detectors in the police helicopter will pick you out even when you think the trees are hiding you, because you’re warmer than they are. Thermal infrared imagers are detector and lens combinations that give a visual representation of infrared energy emitted by objects. Thermal infrared images let you see heat and how it is distributed.
A thermal infrared camera detects infrared energy and converts it into an electronic signal, which is then processed to produce a thermal image and perform temperature calculations.
Thermal imaging cameras have lenses, just like visible light cameras. But in this case the lens focuses waves from infrared energy on to an infrared sensor array. Thousands of sensors on the array convert the infrared energy into electrical signals, which are then converted into a false-colour image. Too much exposure to the Sun’s infrared gives you sunburn – you’re being slowly cooked on the surface of your skin.
Beyond violet is UV. This image is a digitally enhanced representation of the Sun’s UV fingerprint.
The Sun’s ultraviolet rays have shorter wavelength than visible light, so they carry more energy and penetrate deeper into the skin. Special cells called melanocytes have a pigment, melanin, which turns brown in UV light, so you get nicely suntanned.
Too much exposure to solar UV can set the skin cells off into crazy, random divisions and you can get melanoma, a form of skin cancer. So, cover up or wear SFP 50! This is what happens to your DNA – more or less. The UV radiation behaves like ‘light-bullets’, chipping bits off the delicate double helix structure which gets so badly damaged it can’t repair itself properly.