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Two bodies A and B with equal surface areas are kept at 10 deg C and 20 deg C respectively. In a given time, what is the ratio of the thermal radiation emitted by A to that by B?

1. 1: 1.15
2. 1: 2
3. 1: 4
4. 1: 16

Correct answer: 1: 1.15

Solution

The ratio is (283/293)⁴ ~= 0.87, i.e. about 1: 1.15.

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