The History of Infrared Photography (contd.)
Using a glass prism to refract light from the sun into its
component colors, he moved thermometers through the
spectrum. The temperatures increased as the thermometers
were moved from violet to red and reached a maximum in
the dark region beyond the red end of the visible spectrum.
The Royal Society of London was notified of this discovery in
1800. In his writings, Herschel referred to this phenomenon
as “invisible light”.
Herschel's Prism and Mirror c1800