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GATE 2022 MT – Question 43

Transport Phenomena and Rate Processes · Heat transfer · 2 marks · Multiple select

Which of the following statement(s) is(are) TRUE about black body radiation?

  1. Among all radiation emitted by an ideal black body at room temperature, the most intense radiation falls in the visible light spectrum
  2. The total emissive power of an ideal black body is proportional to the square of its absolute temperature
  3. The emissive power of an ideal black body peaks at a wavelength λ which is inversely proportional to its absolute temperature
  4. The radiant energy emitted by an ideal black body is greater than that emitted by the non-black body at all temperatures above 0 K

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Show answer and explanation

Correct answer: (C) The emissive power of an ideal black body peaks at a wavelength λ which is inversely proportional to its absolute temperature; (D) The radiant energy emitted by an ideal black body is greater than that emitted by the non-black body at all temperatures above 0 K

Explanation

Wien’s law gives $\lambda_{max}T=\text{constant}$, supporting C. A blackbody has maximum emission at a given temperature and area, supporting the intended equal-temperature comparison in D. Room-temperature peak radiation is infrared, and total emissive power scales as $T^4$, so A and B are false. Correct choices: **C, D**.