If infrared light is a type of radiation emmited by atmospheric molecules how is it that the human body ‘glows’ so much more than its surroundings?
In: 4
>If infrared light is a type of radiation emmited by atmospheric molecules
I’m not sure what you mean by this. Perhaps you are thinking of something else, maybe cosmic rays?
Infrared light is radiation emitted by *all matter* that is above absolute zero. The hotter the object the more infrared light it emits.
We humans tend to be hotter than our surroundings, so we “glow” relative to it.
>If infrared light is a type of radiation emmited by atmospheric molecules
I’m not sure what you mean by this. This isn’t what infrared radiation is. Infrared radiation is just the part of the electromagnetic spectrum below visible light. Every single object that’s above absolute zero emits electromagnetic radiation which is called [black body radiation](https://howthingswork.org/physics-qm-black-body-radiation/). The type of radiation that the object emits corresponds to its temperature. Our body temperate (and the temperature of most black body objects that we encounter in our daily lives) is such that we emit in the infrared part of the spectrum.
Infrared “light” is heat. It is energy generated in that portion of the electromagnetic spectrum where the wavelengths are longer than visible light. The body radiates heat as a result of regular bodily functions.
To my knowledge the body does not radiate on other portions of the spectrum such as visible light like fireflies.
Any object warmer than absolute zero (0K) “glows” with electromagnetic radiation. Extremely cold objects in deep space emit radio waves and microwave radiation, while objects in the more “terrestrial” temperature range like you see around you emit infrared radiation. Objects can become hot enough to emit visible light, such as the gases of a candle flame, the filament of an old-fashioned light bulb, and even the Sun itself. This is called Blackbody radiation, it comes from the kinetic energy of vibrating atoms and molecules. A human body glows more than surrounding objects simply because human bodies are often warmer than the things around them. Everything else is still emitting infrared light, just with less energy overall.
Black body radiation
All matter that has temperature (ie not at absolute zero) will emit light. Humans are cool enough that we don’t emit visible light, but we do emit infrared light.
When you heat something up red hot, that just means it’s hot enough that it can emit red light. When something is white hot, it’s hot enough to emit all colors of visible light.
We can tell how hot the surface of distant stars are by just looking at what colors of light it gives off. Red is the coolest, then yellow, then white, then blue being the hottest. We also consider infrared, UV, and x-rays when measuring the temperature.
The IR thermometers you may have become familiar with during covid use this fact to measure the temperature of humans quickly and efficiently. It just compares the intestity of different infrared frequencies so we can quickly differentiate between a human at 98°F and one at 100°F. It’s not as accurate as an oral thermometer, but it’s faster and cleaner.
Latest Answers