Infra-red Radiation and William Herschel

Aims Know the properties of infra-red radiation Explain how Herschel discovered infra-red radiation.

EM Radiation: Uses: Dangers: Infrared Remote controls (TV/VCR), radiant heaters, grills, optical fibre communication, night vision. Skin burns

Which are the hottest/coolest parts of the image shown? Night vision Which are the hottest/coolest parts of the image shown? All objects above absolute zero emit infrared radiation. The hotter an object is, the more heat radiation it emits. Some animals and cameras can detect infrared radiation and are able to build up a heat picture. light is hot dark is cold

1 Frozen chickens

2 House insulation Baby in incubator

Sir Frederick William Herschel Discovered the planet Uranus and 2 of its moons in 1781. Discovered Infrared radiation in1800. Discovered two moons of Saturn. Sir Frederick William Herschel (15 November 1738 – 25 August 1822)

He measured the temperature of different colors of the spectrum by placing a thermometer on each colour. He found to his amazement that the hottest part of the spectrum was in a place where there was no colour at all. It was a region beyond the red end of the spectrum. For the first time it was possible to talk about invisible light. This hot light became known as Infrared (below the red) because it was shown to have longer wavelength than visible light.