## Wien;s Law

Wien's displacement law relates the wavelengthat which the intensity of radiation from a black body source is a maximum to the absolute temperatureof the black body. Wien's law states

The value of the constant (units m K) is determined by experiment.

We can analyse light from a star and calculate a value for it's surface temperature using Wien's Law. The spectrum from hotter stars will peak at shorter wavelengths, corresponding to higher temperatures than light from cooler stars.

The dotted curve above illustrates Wien's Law.

Example: The Sun's spectrum peaks at a wavelength of approximately 500nm. Wien's Law gives the temperature of the Sun's surface as approximately