GATE 2021 PH – Question 29
A light source with its intensity peak at wavelength 289.8 nm is calibrated at 10,000 K, the temperature of an equivalent blackbody. Under the same calibration, find the temperature in K for a source peaking at 579.6 nm, rounded to the nearest integer.
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Correct answer: 5000 to 5000
Explanation
Wien’s displacement law gives $\lambda_{\max}T=b$ for the same blackbody calibration. Therefore $T_2=T_1\lambda_1/\lambda_2=10000(289.8/579.6)$. The wavelength has doubled, so the temperature halves to 5000 K.
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