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
If the radius of a star is \(R\) and it acts as a black body, what would be the temperature of the star at which the rate of energy production is \(Q\)? \(\left(\sigma~ \text{is Stefan-Boltzmann constant}\right)\)
1. \(\frac{Q}{4\pi R^2\sigma}\)
2. \(\left(\frac{Q}{4\pi R^2\sigma}\right )^{\frac{-1}{2}}\)
3. \(\left(\frac{4\pi R^2 Q}{\sigma}\right )^{\frac{1}{4}}\)
4. \(\left(\frac{Q}{4\pi R^2 \sigma}\right)^{\frac{1}{4}}\)
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 |
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 |
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. \(5.3\times 10^{8}~\text{K}\)
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
1. | 2. | ||
3. | 4. | Both 1 and 3 |