In spectral radiancy curve for cavity radiation, the wave-length of th...
Explanation:
The spectral radiancy curve for cavity radiation represents the distribution of energy emitted by a black body at different wavelengths. This curve gives us information about the intensity or brightness of the radiation at different wavelengths.
The wavelength at which the maximum spectral radiancy occurs is determined by the temperature of the black body. This is known as Wien's displacement law, which states that the wavelength of maximum spectral radiancy is inversely proportional to the temperature of the black body.
Wien's Displacement Law:
- According to Wien's displacement law, the wavelength of maximum spectral radiancy (λmax) is given by the equation: λmax ∝ 1/T, where T is the temperature of the black body.
- This means that as the temperature increases, the wavelength of maximum spectral radiancy decreases, and vice versa.
Explanation of Option B:
- Option B states that the wavelength of maximum spectral radiancy decreases with increasing temperature. This is the correct answer.
- As per Wien's displacement law, when the temperature of a black body increases, the wavelength of maximum spectral radiancy shifts towards shorter wavelengths, i.e., the radiation becomes bluer.
- This can be observed in everyday life, for example, a heated metal object first starts to glow red, then turns orange, yellow, and finally blue as the temperature increases. The color change is due to the shifting of the wavelength of maximum spectral radiancy towards shorter wavelengths.
Example:
- Let's consider an example to understand this better. Suppose we have two black bodies: one at a temperature of 1000 K and the other at 2000 K.
- According to Wien's displacement law, the black body at 2000 K will have a smaller wavelength of maximum spectral radiancy compared to the black body at 1000 K.
- This means that the black body at 2000 K will emit more energy at shorter wavelengths (bluer light) compared to the black body at 1000 K, which will emit more energy at longer wavelengths (redder light).
Conclusion:
In summary, the wavelength of maximum spectral radiancy for cavity radiation decreases with increasing temperature. This is a direct consequence of Wien's displacement law, which describes the relationship between temperature and the peak wavelength of radiation emitted by a black body.
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