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Sphere 1 with a diameter of 0.1 m is completely enclosed by another sphere 2 of diameter 0.4 m. The view factor F12 is

1. 0.0625
2. 0.25
3. 0.5
4. 1.0

Correct answer: 1.0

Solution

All radiation leaving sphere 1 must strike the completely enclosing sphere 2, so F12 = 1.0. The value 0.0625 is A1/A2 = (0.1/0.4)^2 = F21, not F12. Correct answer is 1.0.

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