Wien's constant is a physical constant that defines the relationship between the thermodynamic temperature of a black body (an object that radiates electromagnetic energy perfectly) and the wavelength at which the intensity of the radiation is the greatest. The constant is denoted by the Greek lowercase letter sigma with a subscript w ( w ). It is equal to approximately 2.898 x 10 -3 meter-kelvin (0.2898 centimeter-kelvin).
The product of the thermodynamic temperature of a black body in kelvin s, and the wavelength of its peak energy output in meter s, is equal to Wien's constant. Thus, as a black body grows hotter, the wavelength of its peak energy output grows shorter, as shown in the illustration.
Also see Table of Physical Constants .