Sir Frederick William Herschel
Infrared light was discovered in 1800 by Sir Frederick William Herschel. Herschel, born in Hanover, Germany, decided to investigate the temperature of each color of the spectrum produced when sunlight is passed through a prism. To do this, he used three thermometers whose bulbs he blacked out (the better to absorb heat with). He placed one bulb directly in the color and the other two past the spectrum to act as controls. Herschel noticed two trends, first that the temperature of the thermometer placed in the color was greater than the controls. The second trend was a temperature increase from violet to red.
Another remarkable observation made by Herschel was when he noticed that the temperature of the region just beyond the red part of the spectrum was even higher than the red itself! He dubbed this radiation "calorific rays." Herschel carried out further experiments in which he demonstrated that what is now known as infrared radiation can be absorbed, transmitted, reflected, and refracted.[Back to Marshall Fellowship]