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Two spheres of the same material have radii 1 m and 4 m and temperatures 4000 K and 2000 K respectively. Find the ratio of the energy radiated per second by the first sphere to that by the second.

1. 1: 1
2. 16: 1
3. 4: 1
4. 1: 9

Correct answer: 1: 1

Solution

Energy per second is proportional to r² * T⁴; the ratio equals (1*4000⁴)/(16*2000⁴) = 16/16 = 1.

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