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Question
A pinhole is made in a hollow sphere of radius 5 cm whose inner wall is at temperature 727oC. Find the power radiated per unit area. [Stefan’s constant σ = 5.7 x 10-8 J/m2 s K4 , emissivity (e) = 0.2]
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Solution
Given:-
T = 727 + 273 = 1000 K,
σ = 5.7 x 10-8 J/m2sK4, e = 0.2
To find:- Power radiated (E)
Formula:-
`(E)Q/(At)=sigmaeT^4`
Calculation:- From formula,
E = 0.2 x 5.7 x 10-8 x (1000)4
= 11400
∴ E = 1.14 x 104 watt/m2
The power radiated per unit area is 1.14 x 104 watt/m2.
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