black body radiation problem
if a black body absorbs and emits all the electromagnetic radiation then what is the diff b/w a black body and a mirror(i think it also does the same).
Replies
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TheBugInYouHow is it stated, that a mirror can absorb/emit electro-magnetic radiation?
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robo_warriorit reflect the EM radiations which is incident on it same
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silverscorpionA black body absorbs all incident electromagnetic radiation on it, irrespective of the frequency or the angle of incidence. At thermal equilibrium, it also emits a radiation known as 'black body radiation'.
Now, assuming you are talking about a glass mirror, it doesn't absorb any radiation. It 'reflects' light. Light is but a tiny fraction of the spectrum of electromagnetic radiation, and only that is reflected. Frequencies outside the visible light spectrum just pass through a mirror. So, how can a mirror and a black body be compared at all? -
zaveri#-Link-Snipped-#
actually there is a lot of difference between a black body and a mirror.
Black body : absorbs radiation completely.
mirror: it is a completely reflective body, and does not absorb any energy or radiation. -
nibhanimirror
mirror doesn't absorb radiation it reflect all of radiation..and black body absorbs all of radiation that is ideal case and not possible in practical life...robo_warriorif a black body absorbs and emits all the electromagnetic radiation then what is the diff b/w a black body and a mirror(i think it also does the same). -
Ramani Aswath
The error is in that part of the definition,'...emits all the electromagnetic radiation...'robo_warriorif a black body absorbs and emits all the electromagnetic radiation then what is the diff b/w a black body and a mirror(i think it also does the same).
An ideal black body radiates energy in the frequency defined by the Planck Law.
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However it will absorb all frequencies incident on it. It is a different matter that such absorption may raise the temperature of the black body making it re radiate energy . However this re radiation will be in a frequency spectrum defined by the Planck law.
A reflector on the other hand just throws back whatever that falls on its surface. A coloured reflector will absorb the complimentary colours to its colour. A red reflector will absorb green frequencies. -
SYED BASEERULLAHDEFINITION OF BLACK BODY IS that it will absorb all incident radiation and then it will give up all the radiations .
In case of mirror only phenomenon of reflection takes place and not absorption.
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