hw4_s09 - -2 μm-1 from the earth’s surface over the 2μm...

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ABE 4034 Homework Problems – 4 Due Date –Thurs 2/5/09 1. Suppose that we measure the emitted exitance from a small hole in a furnace to be 22.8 W/cm 2 , using an optical pyrometer of some sort. Compute the internal temperature of the furnace. 2. When the Sun’s spectrum is photographed, using rockets to range above the Earth’s atmosphere, it is found to have a peak in its spectral exitance at roughly 465 nm. Compute the Sun’s surface temperature, assuming it to be a blackbody. 3. Plot the reflected, emitted, and total spectral power density (Wm
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Unformatted text preview: -2 μm-1 ) from the earth’s surface over the 2μm to 10μm spectral region. Consider cases of the surface with reflectivity equal to 0.1, 0.5, and 0.9. Assume that the sun is a blackbody with a temperature of 6000K, and that the sun’s power density is reduced by a factor of 66790 from the sun to the earth. The earth is an opaque, gray body with a temperature of 300K. Neglect effects of the atmosphere. For all the three cases, find the wavelength at which the emitted and the reflected power densities are the same....
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