Scientists Say: Infrared

This is a wavelength of light beyond what people can see


This is an image of a person taken with an infrared camera. It indicates where the person’s skin is warmer (red and orange) and cooler (green and blue).


Infrared (noun, “IN-frah-red”)

This is a category of light ranging in longer wavelengths from about 800 nanometers to one millimeter (that’s 0.00003 to 0.04 inch). Radiation, including visible light, comes in waves of different lengths. Some of those lengths — including infrared — are too long for our eyes to perceive them. Infrared light gets its name from the fact that these wavelengths are a bit longer than what we see as the color red. Though people cannot see infrared light, some snakes, mosquitoes and other animals can.

Everything emits a tiny bit of light. It’s not visible to the human eye because it is in the infrared spectrum. But the type and amount of light emitted changes with temperature. So animals or technologies that can perceive infrared can also see how hot or cold something is. Scientists can learn a lot about objects by sensing their temperature. For example, infrared cameras can help scientists understand what faraway planets are made of.

In a sentence

An infrared camera could help detect hidden weapons.

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Editor’s note: This post was updated on September 11, 2018 at 9:35 AM EST to correct the conversion from nanometers and millimeters to inches. 

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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