Question

What is perfectly black body? How can it be realized in practice?

Answer 1

Answer:

A body which completely absorbs all heat radiation incident on it is called perfectly black body.

A perfectly black body can not be realised in practice but materials like Platinum black or Lamp black come close to being ideal black bodies. Such materials absorbs 96% to 85% of the incident radiations.

Answer 2

A perfectly black body is nothing but a body on which all the radiant energy projected on it gets completely absorbed.

Detailed answer

In a perfectly black body, there is almost zero reflection as the radiant energy gets completely absorbed between the walls.

• There is no perfect black body currently that exists in our world.
• Lampblack or platinum black is the best black body that exists and they absorb almost 97% of the radiant energy projected on it.
• Ferry's black body is an example of a perfectly black body it is made of a hollow metal sphere that is coated with lamp black on the inside, it has a small apperture
• A perfectly black body cannot be realized in practice but some of the above stated come close to being realized as one.
• The sun is an example of a perfectly black body.