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Calculate the amount of heat radiated per second by a body of surface area `12cm^(2)` kept in thermal equilibrium in a room at temperature `20^(@)C` The emissivity of the surface `=0.80` and `sigma=6.0xx10^(-s)Wm^(-2)K^(-4)` .

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The correct Answer is:
B, D
`A=12 cm^(2)=12xx10^(-4)m^(2),`
`T=20^(@)C=293^(@)K,`
`sigma=6xx10^(-8)W//m^(2)-K^(4)`
`Q=AeST^4` ltbrge12xx10^(-4)xx0.8xx6xx10^(-8)xx(293)^4`
`=0.4245=0.42`.
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