PHYS 2004 Lecture Notes - Lecture 4: Black-Body Radiation, Black Body, Emissivity
16 Nov 2017
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Document Summary
An object with surface area a and absolute temperature t radiates heat energy at the rate: where = 5. 67 10 8 w/m2 k4 is the stefan-boltzmann constant. The parameter e is the emissivity of the surface. A perfectly absorbing and thus perfectly emitting object with e = 1 is called a blackbody, and the thermal radiation emitted by a blackbody is called blackbody radiation. If we measure the spectrum of a blackbody at three temperatures, 3500 k, 4500 k, and 5500 k, the data appear as shown. All blackbodies at the same temperature emit exactly the same spectrum. Increasing the temperature increases the radiated intensity at all wavelengths. Increasing the temperature causes the peak intensity to shift toward shorter wavelengths.
