Question

An ideal black body at room temperature is thrown into a furnace. It is observed that________.

• A. it is the darkest body at all times
• B. it cannot be distinguished at all times
• C. initially, it is the darkest body and at later times the brightest
• D. initially, it is the darkest body and at later times it cannot be distinguished

Answer 1

The correct option is C

initially, it is the darkest body and at later times the brightest

1. A body that absorbs all the radiant energy incident upon it and reflects or transmits none is called an ideal black body.
2. An ideal black body is a good emitter and good absorber.
3. Initially, it will absorb all the energy and will appear dark.
4. As soon as it attains the temperature equal to that of the furnace, it will start emitting radiation greater than the rest of the furnace and hence appears the brightest.

Hence, the answer is (C) initially, it is the darkest body and at later times the brightest.