Statement: A black body is an ideal absorber and emitter of radiation.
Conclusion I: Radiation is not reflected from a black body.
Conclusion II: A black body emits more energy at a high temperature.
Choose the correct conclusion of the given statement:
- AOnly conclusion I is correct
- BOnly conclusion II is correct
- CBoth conclusions are correct
- DNeither conclusion is correct
Show answer and explanation
Correct answer: (c) Both conclusions are correct
Explanation
A black body absorbs all the radiation that falls on it, so it reflects none (Conclusion I is correct). A good absorber is also a good emitter, so a black body is also the ideal emitter.
The energy it radiates per unit area per second follows the Stefan–Boltzmann law, E = σT⁴. The emission rises steeply with temperature, so a black body emits more energy at a higher temperature (Conclusion II is correct). Its peak wavelength also shifts to shorter wavelengths as it gets hotter (Wien's law).