Taking into account the radiation that a human body emits which of the following statements is true?
1. | The radiation is emitted only during the day. |
2. | The radiation is emitted during the summers and absorbed during the winters. |
3. | The radiation emitted lies in the ultraviolet region and hence is not visible. |
4. | The radiation emitted is in the infra-red region. |
According to Wein's law:
1. = constant
2. = constant
3. = constant
4. = constant
A black body at \(200\) K is found to emit maximum energy at a wavelength of \(14\) \(\mu \)m. When its temperature is raised to \(1000\) K, the wavelength at which maximum energy is emitted will be:
1. | \(14\) \(\mu \)m | 2. | \(70\) \(\mu \)m |
3. | \(2.8\) \(\mu \)m | 4. | \(2.8\) nm |
If the temperature of the sun becomes twice its present temperature, then:
1. | Radiated energy would be predominantly in the infrared range. |
2. | Radiated energy would be primarily in the ultraviolet range. |
3. | Radiated energy would be predominantly in the X-ray region |
4. | Radiated energy would become twice as strong as it is now. |
A black body has a maximum wavelength at a temperature of 2000 K. Its corresponding wavelength at temperatures of 3000 K will be:
1. | \({3 \over 2} \lambda_m\) | 2. | \({2 \over 3} \lambda_m\) |
3. | \({4 \over 9} \lambda_m\) | 4. | \({9 \over 4} \lambda_m\) |
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
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 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. \(5.3\times 10^{8}~\text{K}\)
Consider two hot bodies, and which have temperatures of \(100^{\circ}\mathrm{C}\) and \(80^{\circ}\mathrm{C}\) respectively at t=0. The temperature of the surroundings is \(40^{\circ}\mathrm{C}\). The ratio of the respective rates of cooling and of these two bodies at t = 0 will be:
1.
2.
3.
4.
Three rods of identical area of cross-section and made from the same metal form the sides of an isosceles triangle ABC, which is right-angled at B. The points A and B are maintained at temperatures T and respectively. In the steady state, the temperature of point C is . Assuming that only heat conduction takes place, is equal to:
1.
2.
3.
4.