Which type of electromagnetic wave is formed because of heat?

• A. Visible light
• B. Microwaves
• C. Infrared
• D. Radio waves

Answer: (C)

Heat causes thermal radiation: as an object’s temperature rises, its charged particles jiggle and emit photons. At ordinary temperatures, most of this emission falls in the infrared part of the spectrum, which is exactly the range we associate with warmth. You feel infrared radiation as heat even if you can’t see it. Only at very high temperatures does the emission shift into visible light, which is why heated metal can glow red, orange, or white. Microwaves and radio waves come mainly from specialized devices and circuits, not just from heat itself. So infrared is the best match for radiation formed because of heat.