Q134 / 150 · MHT CET 2026 (15 April Shift 1) · Physics
About black body radiation, which one of the following is a WRONG statement?
- Correct answerAFor all wavelengths, power radiated is same
- BFor shorter wavelengths, radiated power is more
- Cfor longer wavelengths, radiated power is less
- DAll wavelengths are emitted by the black body
Solution
According to the spectral distribution of black body radiation (Planck's law), a black body emits radiation of all possible wavelengths, but the energy is not uniformly distributed among them.
The spectral emissive power ($E_{\lambda}$) first increases with an increase in wavelength, reaches a maximum value at a specific wavelength ($\lambda_{m}$), and then decreases for longer wavelengths.
Therefore, the statement "For all wavelengths, power radiated is same" is completely incorrect.
Answer: For all wavelengths, power radiated is same
The spectral emissive power ($E_{\lambda}$) first increases with an increase in wavelength, reaches a maximum value at a specific wavelength ($\lambda_{m}$), and then decreases for longer wavelengths.
Therefore, the statement "For all wavelengths, power radiated is same" is completely incorrect.
Answer: For all wavelengths, power radiated is same
Hence, the correct answer is option: 'A'.