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 •Suppose
 a brown-out causes the temperature of a lamp filament to drop to 0.9 of its original value.  By what factor does the light output of the lamp drop?
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 •
 •Using
 the Stefan-Boltzmann law (with the numerical value of s) we could have calculated how big (in m2) a light filament would have to be to emit 100 W of light, at any given temperature.
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 •We
 could also use it to find the size of a star, if we know how much light energy that star emitted