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Q. No.A radiation blackbody has the shape of a sphere of radius \(r.\) Its surface is at a temperature \(T\) (in Kelvin). If the temperature is doubled and the radius is halved, the total rate of radiation emitted from the body:
| 1. | increases by a factor of \(4\) |
| 2. | increases by a factor of \(2\) |
| 3. | remains unchanged |
| 4. | decreases by a factor of \(2\) |
Subtopic: Stefan-Boltzmann Law |
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Ice (\(0^{\circ}\)C) is kept in an insulated reservoir with an opening that is covered at the top with a cloth. When a black cloth \((B)\) is placed at the top, the ice melts at \(2\) g/\(3\) min. When an ordinary cloth \((G)\) is placed, the rate of melting is \(2\) g /\(5\) min. The emissivity of \(G\) is: (assuming that \(B\) behaves as a blackbody)
| 1. | \(0.6\) | 2. | \(0.3\) |
| 3. | \(0.4\) | 4. | \(0.5\) |
Subtopic: Stefan-Boltzmann Law |
74%
From NCERT
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A solid at temperature T1, is kept in an evacuated chamber at temperature T2 > T1 . The rate of increase of temperature of the body is proportional to
1. T2 – T1
2. \(T^2_2 -T^2_1\)n
3. \(T^3_2 -T^3_1\)
4. \(T^4_2 -T^4_1\)
Subtopic: Stefan-Boltzmann Law |
80%
From NCERT
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A black body at \(227^{\circ}~\mathrm{C}\) radiates heat at the rate of \(7~ \mathrm{cal-cm^{-2}s^{-1}}\). At a temperature of \(727^{\circ}~\mathrm{C}\), the rate of heat radiated in the same units will be:
1. \(60\)
2. \(50\)
3. \(112\)
4. \(80\)
Subtopic: Stefan-Boltzmann Law |
86%
From NCERT
AIPMT - 2009
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