# emissivity and radiation

A.) The filament of a light bulb has a temperature of 3.1 103 °C and radiates 70 watts of power. The emissivity of the filament is 0.38. Find the surface area of the filament.

B.) A car parked in the sun absorbs energy at a rate of 550 watts per square meter of surface area. The car reaches a temperature at which it radiates energy at this same rate. Treating the car as a perfect radiator (e = 1), find the temperature.

C.) A person eats a dessert that contains 210 Calories. The skin temperature of a person is 36°C and that of her environment is 20°C. The emissivity of her skin is 0.75 and its surface area is 1.3 m2. How much time would it take for her to emit a net radiant energy from her body that is equal to the energy contained in this dessert?

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A) The filament of a light bulb has a temperature of 3.1 103 °C and radiates 70 watts of power. The emissivity of the filament is 0.38. Find the surface area of the filament.

According to Stefan-Boltzmann law,

Where the constant

The emissivity e = 0.38

The temperature ...

#### Solution Summary

It provides examples of finding the light radiation and emissivity. The solution is detailed and well presented.