And why and how does it represent heat unlike other wavelengths of light?
In: 0
[removed]
“Infra-” means “below”. Infrared just means light that’s less energetic than visible red light.
> And why and how does it represent heat unlike other wavelengths of light
Everything that’s hotter than absolute zero gives off light. That’s why fire glows red or blue, and why metals glow when heated. It’s just very rare for things to actually get hot enough to glow visibly. And light that is less energetic than visible light is infrared, hence infrared is associated with heat.
It’s just at a wavelength that doesn’t tickle our eye structures (rods/cones). The thing about heat is that any object that is above absolute zero in temperature will emit “blackbody radiation.” The more energy it has, the brighter the radiation. When looking at a human, our blackbody radiation is in the infrared part of the EM spectrum.
I knew it would be in the visible spectrum that we can see at a certain temp. I looked that up, and it’s called the Draper temperature, which is 798 Kelvin which is ~525C or 977F. Once an object is that temperature, we can see it glow. Yikes for Rudolph.
It is not different, it’s just below (infra) visible red in wavelength.
Hot things radiate IR, but if you heat it more it radiates other colors as well, this is called black body radiation. Think about a smith heating metal, or an incandescent bulb heating its tungsten wire.
Infrared is merely light that our eyeballs did not evolve to detect. The frequency is too low. Much like a frequency of sound that is too low to hear. Otherwise, it acts just like any other frequency of light.
Infrared light happens to be able to impart its energy to things very well without bouncing off or being so energetic it destroys them (See UV-C). When this happens, this energy is perceived as “heat” as “heat” is a measure of energy in a system.
There is only “hot” and “not hot.” “Cold” is the absence of heat. That is, the absence of energy in a system.
IR behaves much like visible light. It is a bit more prone to passing through things, though, and is much less able to chemically alter substances. This makes it harder to photograph with.
IR is a pretty big range, and is roughly divided into near-IR and far-IR. Far-IR is more like radio waves, while near-IR is more like visible light.
It represents heat because of something called blackbody radiation. All objects glow, and their glow has a different frequency based on temperature. At all temperatures we normally encounter, up to 500c or so, that glow is mainly in IR. At higher temperatures it becomes visible, but there is still a lot of IR.
Infrared is just a longer wavelength of light than the visible we see.
https://en.m.wikipedia.org/wiki/Electromagnetic_spectrum
As to why we say it’s “heat”, that goes back to anything with a temperature above absolute zero will give of light called black body radiation.
https://en.m.wikipedia.org/wiki/Black-body_radiation
The stuff around us that’s around room temperature or say your body temperature gives off this light in the infrared spectrum. So we need special cameras to see this light. If you heat something up hotter and hotter the black body radiation will slowly move into the visible range starting at red and moving to white. If you have an electric stove you can kinda of see this as the coils start to glow bright red (although it won’t get hot enough to go past red).
it isn’t different from any other light.
It carries energy from point A to point B.
Objects produce light (of all colors) by having a temperature. The hotter it is, the more of all light, but also the higher “peak” energy. So a cool object produces a little bit of everything, but mostly radio. Warm it up to what we consider “hot” and it gives more of everything, but peaks in Infrared. And so on.
Infrared does have one general trait other wavelengths don’t have.
Radio and microwave are to long to interact with most atoms and molecules, and pass through.
Infrared tends to have the right amount of energy to interact with many molecular bonds, and so is easily absorbed by living organisms, transfering the energy into the molecules, which vibrate more (which is heat). But the vibration isn’t always enough to actually do much to the molecule.
Higher energy light tends to pass through molecules rather than interact. This is basically a resonance effect, sort of how a musical instrument only makes one note at a time on a string.
So while higher energy light can, and does, transfer the energy into organic material it often triggers more than just vibrations causing it to warm up. It can trigger chemical reactions as the higher energies can actually cause molecules to vibrate hard enough to rip apart, or strip electrons off atoms etc.
Latest Answers