Question

Use the formula ${\lambda }_m$T = 0.29 cm K to obtain the characteristic temperature ranges for different parts of the electromagnetic spectrum. What do the numbers that you obtain tell you?

Answer 1

A body at temperature T produces a continuous spectrum of wavelengths. For a black body, the wavelength corresponding to maximum intensity of radiation is given according to Planck's law by the relation, $m=0.29cmK/T$. For $m={10}^{6}m,T=2900K$.Temperatures for other wavelengths can be found. These numbers tell us the temperature ranges required for obtaining radiations in different parts of the electromagnetic spectrum. Thus, to obtain visible radiation, say $=5\times {10}^{7}m$, the source should have a temperature of about $6000K$. A lower temperature will also produce this wavelength but not the maximum intensity.