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. |
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Which of the following is closest to an ideal black body?
1. | Black lamp |
2. | Cavity maintained at a constant temperature |
3. | Platinum black |
4. | A lump of charcoal heated to high temperature |
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On a clear sunny day, an object at temperature T is placed on the top of a high mountain. An identical object at the same temperature is placed at the foot of the mountain. If both the objects are exposed to sun-rays for two hours in an identical manner, the object placed on the top of a mountain will register a temperature:
1. | higher than the object at the foot. |
2. | lower than the object at the foot. |
3. | equal to the object at the foot. |
4. | none of the above. |
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