Multiple choice

The energy radiated per second by a spherical black body will be double, if its

  1. radius is increased by nearly 41.5 %

  2. radius is doubled

  3. radius is increased by nearly 44.5 %

  4. none of these
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A Correct answer
Explanation

Radiated power is proportional to surface area, which for a sphere is 4 * pi * r^2. To double the power, the area must double, requiring the radius to increase by a factor of sqrt(2) (approx. 1.414), which is a 41.4% increase.

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