Question

What is BLACK BODY?

What is BLACK BODY RADIATION?

Is there any black body really exist?

Thanks :)

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Answer 1

A blackbody (sometimes spelled "black body") is a theoretically ideal radiator and absorber of energy at all electromagnetic wavelength s. The term comes from the fact that a coldblackbody appears visually black. The energy emitted by a blackbody is called blackbody radiation.

no there any black body doesnt exist

Answer 2

BLACK BODY:
=> An Ideal perfect absorber of energy with no reflecting power.

Q:
Why it has no reflecting power?
No Reflecting power cause it is absorbing 100% energy incident on it in.

Standard Definition :
=>Idealized Physical Body that absorbs all incident energy (in form of EM waves) , regardless of frequency or angle of incidence.
Source : NCERT
Chemistry : Atomic Structure
Physics : Heat Transfer

Black Body Radiation :
=> At constant temperature, Black body emits Electromagnetic Radiation called Black Body Radiation.

Is there really black body exists.
No, there is no black body cause no body absorbs 100% energy entirely incident on it.

=> But, wait this doesn't mean there is no body which absorbs radiations.
There exists body which absorbs radiations but along with it they reflect some radiations too which is not the case in Black body cause it is 100% absorber of energy ,no reflection.

Now,
People here thought that If there is Black Body Radiation then Black Body is reflecting some radiations naa.

Then why it is called Black body and 100% absorber?
=> There is difference between emitting of radiations and reflecting of radiations.
=> It emits at constant temperature that is when it is in Thermal Equilibrium at its own.
Not from any incident energy.

=>When Energy is incident., it's temperature changes and cant radiations at that time.