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MHT CET 2023 (12 May, Shift 2) · Thermal Radiation: Black Body, Stefan & Wien

Thermal Radiation: Black Body, Stefan & Wien question from MHT CET 2023 (12 May, Shift 2)

Q79MHT CET 2023 · 12 MAY · SHIFT 2Medium

Thermal Radiation: Black Body, Stefan & Wien

Compare the rate of loss of heat from a metal sphere at 627∘C627^\circ\text{C} with the rate of loss of heat from the same sphere at 327∘C327^\circ\text{C}, if the temperature of the surrounding is 27∘C27^\circ\text{C}. (nearly)

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Answer: (b)

  1. Net rate of heat loss ∝T4−T04\propto T^4 - T_0^4, with T0=300 KT_0 = 300\text{ K}.
  2. T1=900 K=3T0T_1 = 900\text{ K} = 3T_0, T2=600 K=2T0T_2 = 600\text{ K} = 2T_0.
  3. Q1Q2=34−124−1=8015≈5.3\frac{Q_1}{Q_2} = \frac{3^4 - 1}{2^4 - 1} = \frac{80}{15} \approx 5.3
  4. So the answer is (b) 5.3.
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