Why does black color asorb light?

[ehild]

As we know that energy can neither be created nor destroyed then the light absorbed by a blackbody has to leave the body in some form or the other.. If u say a black body just keeps on absorbing light then that means that the temperature of the blackbody will keep on increasing with time...There would be something happening with the light falling on it..What is that after absorption of light happens with EM rays..

You are right, the body will not warm up infinitely: it also loses energy.
The loss of energy can happen

by induced emission, when the body emits photons of the same wavelength and direction as the absorbed ones, but the probability of induced emission is very low in ordinary bodies.

by by spontaneous emission: the wavelength is the same, but the direction of the emitted photon is random

the absorbed radiation energy is converted to the random motion of the atoms and electrons, increasing the internal energy of the object, that is, increasing temperature. The body radiates according to its temperature and its material. The temperature increases till equilibrium is reached: the rate of absorption balances the rate of radiation.


ehild

 

[Claude Bile]

@Claude Bile: Do u mean to indirectly say that black is also emitting a wavelength which is outside Visible range and occupies some other EM spectrum. If you are saying so, i feel that you are denying the real definition of Black. "Black is something that absorbs all color",..so if something absorbs all color how can it reflect anything..And as per the experiments done since time in memorial "Black doesn't reflect any thing..It does emit different rays as per its temperature"..

Well, it depends what you define as being "black". In everyday life "black" means "none of my color receptors are being stimulated". Even the night sky has a long wavelength glow to it. Occasionally in physics we might define black as encompassing all wavelengths, such as in black body radiation. Whatever the case, the moral of the story here is to be explicit by what is meant when you describe something as "black".

@sophiecentaur: I hadn't realized this, good to know!

Claude.