The earth radiates in the infra-red region of the spectrum. The spectrum is correctly given by (a) Rayleigh Jeans law (b) Planck's law of radiation (c) Stefan's law of radiation (d) Wien's law

Answer: (d). Earth's temperature is about 300 K, so by Wien's law λm = b/T ≈ 2.9 × 10⁻³300 ≈ 10, which is in the infra-red. The key uses Wien's law to explain why the earth's radiation lies in the infra-red. So the answer (as per key) is (d) Wien's law.

The earth radiates in the infra-red region of the spectrum. The… | JEE Main 2003 (AIEEE)

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Thermal Radiation: Black Body, Stefan & Wien

The earth radiates in the infra-red region of the spectrum. The spectrum is correctly given by

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Answer: (d)

Earth's temperature is about 300 K, so by Wien's law $\lambda_m = \dfrac{b}{T} \approx \dfrac{2.9 \times 10^{-3}}{300} \approx 10\ \mu\text{m}$ , which is in the infra-red.
The key uses Wien's law to explain why the earth's radiation lies in the infra-red.
So the answer (as per key) is (d) Wien's law.

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