- 1(current)
Q. No.Given below are two statements:
| Assertion (A): | For small difference in absolute temperature, compared with the temperature itself, the net rate of transfer of energy from a body to its surrounding by radiation is directly proportional to the temperature difference. |
| Reason (R): | The net ratio of transfer of energy by radiation from a body (temperature \(T_b=T_S+\theta\)) to its surrounding (temperature \(T_S\)) is given by: \(\dfrac{dQ}{dt}=eA\sigma(T_b^4-T_S^4)\\ ~~~~~~~=eA\sigma\left\{(T_S+\theta)^4-T_S^4\right\}\\ ~~~~~~~\approx4eA\sigma T^3_S\theta,~\text{where }\theta\ll T_S.\) |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True but (R) is False. |
| 4. | (A) is False but (R) is True. |
Subtopic: Radiation |
82%
Level 1: 80%+
Hints
If the absolute temperature of a star doubles but its radius halves, then the rate of radiation from the star:
1. increases \(4\) times
2. increases \(2\) times
3. remains unchanged
4. decreases \(2\) times
1. increases \(4\) times
2. increases \(2\) times
3. remains unchanged
4. decreases \(2\) times
Subtopic: Radiation |
76%
Level 2: 60%+
Hints
A steel rod, insulated at its sides, is inserted into a high temperature oven – as shown in the figure. The end of the rod is blackened and is observed to be at a temperature \(T_b,\) and the temperature of the surroundings is \(T_S.\) The conductivity of steel is \(K,\) and Stefan's constant is \(\sigma.\) The temperature of the oven is (all temperatures are on absolute scale):
| 1. | \(T_S+\dfrac{L\sigma}{K}T_b^4\) | 2. | \(T_b+\dfrac{L\sigma}{K}(T_b-T_S)^4\) |
| 3. | \(T_b+\dfrac{L\sigma}{K}(T_b^4-T_S^4)\) | 4. | \(\left\{T_b^4+\dfrac{L\sigma}{K}(T_b^4-T_S^4)\right\}^{1/4}\) |
Subtopic: Radiation |
63%
Level 2: 60%+
Hints
- 1(current)
Q. No.
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