Question
What is perfectly black body? Explain Ferry's black body.
✓
Answer
A perfectly black body which absorbs all the energy incident on it. The coefficient of absorption of lamp black is 98%.
(i) It consist of double walled hollow metal sphere having small aperture.
(ii) Inner surface is coated with lamp black.
(iii) Outer surface is Nickel polished.
(iv) The space between sphere is evacuated.
(v) The radiant energy entering suffers multiple reflection and get 98% absorbed at each reflection.
(vi) Thus the aperture acts as perfectly black body.
(i) It consist of double walled hollow metal sphere having small aperture.
(ii) Inner surface is coated with lamp black.
(iii) Outer surface is Nickel polished.
(iv) The space between sphere is evacuated.
(v) The radiant energy entering suffers multiple reflection and get 98% absorbed at each reflection.
(vi) Thus the aperture acts as perfectly black body.
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