- 1(current)
Q. No.If the temperature of the body is increased from \(-73^{\circ}\mathrm{C}\) to \(327^{\circ}\mathrm{C}\), then the ratio of energy emitted per second in both cases is:
1. 1 : 3
2. 1 : 81
3. 1 : 27
4. 1 : 9
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| 1. | \(\dfrac{Q}{4\pi R^2\sigma}\) | 2. | \(\left(\dfrac{Q}{4\pi R^2\sigma}\right )^{\dfrac{-1}{2}}\) |
| 3. | \(\left(\dfrac{4\pi R^2 Q}{\sigma}\right )^{\dfrac{1}{4}}\) | 4. | \(\left(\dfrac{Q}{4\pi R^2 \sigma}\right)^{\dfrac{1}{4}}\) |
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The rate of heat emission from an ideal black body at temperature T is H. What will be the rate of emission of heat by another body of same size at temperature 2T and emissivity 0.25?
| 1. | 16 H | 2. | 4 H |
| 3. | 8 H | 4. | 4.5 H |
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A spherical black body with a radius of \(12\) cm radiates \(450\)-watt power at \(500\) K. If the radius were halved and the temperature doubled, the power radiated in watts would be:
1. \(225\)
2. \(450\)
3. \(1000\)
4. \(1800\)
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If the sun’s surface radiates heat at \(6.3\times 10^{7}~\text{Wm}^{-2}\) then the temperature of the sun, assuming it to be a black body, will be:
\(\left(\sigma = 5.7\times 10^{-8}~\text{Wm}^{-2}\text{K}^{-4}\right)\)
1. \(5.8\times 10^{3}~\text{K}\)
2. \(8.5\times 10^{3}~\text{K}\)
3. \(3.5\times 10^{8}~\text{K}\)
4. \(5.3\times 10^{8}~\text{K}\)
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The temperature of an object is \(400^{\circ}\mathrm{C}\). The temperature of the surroundings may be assumed to be negligible. What temperature would cause the energy to radiate twice as quickly? (Given, \(2^{\frac{1}{4}} \approx 1.18\))
1. \(200^{\circ}\mathrm{C}\)
2. \(200\) K
3. \(800^{\circ}\mathrm{C}\)
4. \(800\) K
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| 1. |  |
2. |  |
| 3. |  |
4. | Both 1 and 3 |
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- 1(current)
Q. No.
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