Question
(a) Calculate the rate in watts at which heat transfer through radiation occurs (almost entirely in the infrared) from $1.0 \textrm{ m}^2$ of the Earth’s surface at night. Assume the emissivity is 0.90, the temperature of the Earth is $15^\circ\textrm{C}$, and that of outer space is 2.7 K. (b) Compare the intensity of this radiation with that coming to the Earth from the Sun during the day, which averages about $800 \textrm{ W/m}^2$, only half of which is absorbed. (c) What is the maximum magnetic field strength in the outgoing radiation, assuming it is a continuous wave?
1. $-350 \textrm{ W}$
2. 88% of solar radiation absorbed during the day is re-emitted at night.
3. $1.7 \times 10^{-6} \textrm{ T}$
Solution Video