Blackbody Radiation Relating Heat and Light—Part II

BLACKBODY RADIATION RELATING HEAT AND LIGHT—PART II 

FIGURE 10.1 (a) The radiative power emitted by a blackbody at various temperatures illustrates Wein s Law. 

In relation to the introductory thermodynamic equations of the Stefan-Boltzmann law we note that Max Planck had been a professor of physics since 1889 specializing in thermodynamics. There is a very interesting history of Planck s discovery on the Internet at http //www.daviddarling. info/encyclopedia/Q/quantum theory origins.html. In fact Planck s interest was initially related to an equation he had tried to find relating Boltzmann s entropy to Wein s law. Wein s law was simply that the color of a hot object shifts with temperature and Planck developed the quantized equation to explain Wein s law. Wein s law is just an empirical observation that Planck tried to put on a firm foundation, although Planck approached the problem from a thermodynamic approach. Wien s Law relates the wavelength of the spectral maximum to temperature as [7] 

FIGURE 10.2 A schematic of measurement of blackbody radiation from a heated source. 

FIGURE 10.4 A scoreboard to count the energy modes in a radiating blackbody. 

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