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The best ideal black body is (a) Lamp of charcoal heated to high temperature (b) Metal coated with a black dye (c) Glass surface coated with coalter (d) Hollow enclosure blackened inside and having a small hole

The best ideal black body is
(a) Lamp of charcoal heated to high temperature
(b) Metal coated with a black dye
(c) Glass surface coated with coalter
(d) Hollow enclosure blackened inside and having a small hole

Grade:Upto college level

2 Answers

Saurabh Koranglekar
askIITians Faculty 10341 Points
one year ago
Hollow enclosure blackened inside and having a small hole is a very good example of a black body.
Suppose once light enters inside it.
It may be absorbed or it may be reflected.
Since it is blackened from inside, there is a high probability that it will be absorbed.
Now if it is reflected, it will suffer multiple reflections and it is very unlikely that it will come out of the hole because the aperture of hole is too small. Moreover, with each reflection, more and more fraction of it will be absorbed. So, it will serve as a good black body.
Vikas TU
14149 Points
one year ago
Real materials emit energy at a fraction—called the emissivity—of black-body energy levels. By definition, a black body in thermal equilibrium has an emissivity of ε = 1. A source with lower emissivity independent of frequency often is referred to as a gray body.

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