What is blackbody radiation and why does it matter?
In: Physics
Adding to pando93’s excellent answer, black body radiation theory is the simplest and also the first step in order to quantify the natural phenomenon by which literally anything “emits and absorbs light”.
To get a better sense of BBR it’s better to first understand the photoelectric effect.
The photoelectric effect:
It essentially deals with photon – electron interaction. Thanks Einstein.
Photon: the **Super-Duper** lightweight particle light is made of.
Electron: the lightweight negatively charged particle that loves being around the +ve nucleus.
Basically when a photon (light) strikes an atom (of any object gas, liquid or solid or otherwise), the photon “annihilates” itself into pure energy, which is used to knock an electron into an higher “orbit” around the nucleus, or if the photon had enough energy, knock it out of the atom completely. Similarly when a “free” electron falls into “orbit” around the nucleus, it loses energy (potential energy), and this energy becomes a photon and ejects outward at lightspeed.
This is the underlying phenomenon behind everything from the stars and TV screens to fireflies and eyes.
BBR:
Any matter over 0 Kelvin possesses thermal energy, which is in the form of its constituent particles vibrating. This “Vibrational energy” is “used up” to perform the aforementioned knocking-out-the-electrons in the atoms of the said constituent matter into higher “orbit”. And when this energized electron falls back down into it’s appropriate orbit, like a ball tossed into the air, the energy it releases emits as photons.
A cold object will emit low energy light: radio waves and microwaves etc.
Heat an object hot enough and the radiation it emits will become visible radiation. First Red, then red+orange = orangish red, then red+orange+yellow = reddish yellow, then red+orange+yellow+green = brighter yellow, and finally red+orange+yellow+green+blue = the sum of colors = WHITE HOT.
You can still heat it more, and then it will emit UV and X-rays and more higher energy stuff.
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