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A brick wall with a thermal emissivity of 0.8 is heated by the sun all day and is at a temperature of 25 °C in early evening. A pedestrian walking past the wall feels its warmth radiating in to the cool evening air. The wall has surface area of 5m^2. What is the total out put power of the thermal radiation emitted by the wall? Ignore radiation absorbed by the wall from surrounding bodies.

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    (Area)*(sigma)*(0.8)*(298)^4 = ?

    sigma is the Stefan-Bolzmann constant, which you should look up.

    Note the T^4 term, where the temeprature is in Kelvn.

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