Radiant Heat Is Invisible “Infrared” Radiation

As unlikely as it may seem, radiated heat is close kin to radio waves, microwaves, visible light, and X rays. Each of these phenomena is a part of the electromagnetic spectrum, waves of varying energies created by the movement of electrically charged particles, often electrons within atoms. Such movement creates electrical and magnetic fields that radiate, or spread out, as waves. And conversely, when such energetic waves hit other atoms, they cause increased movement in those atoms. One of the first to recognize that heat radiation is related to light was the English oboist and astronomer William Herschel, who noticed in 1800 that if a thermometer was moved from one end of a prism-produced light spectrum to the other, the highest temperatures would register below the red band, where no light was visible. Because of its position in the spectrum, heat radiation is called infrared (infra is Latin for “below”).