Question

8. a) How exactly did Wilhelm Wien enable us to determine the surface temperature of the sun or other stars? What is that procedure for determining (T)? b) The sun's surface temperature is 5,800 K. Using "Wien's displacement law" calculate the peak wave- length emitted, and indicate which part of the spectrum would this calculated wavelength be found.

Answer 1

Wein displacement law states that blackbody spectrum for different temprature peaks for different wavelength.He observed that for a blackbody at a given temprature emits radiation of all wavelength but for particular wavelength of radiation we get the maximum intensity from Intensity-wavelength curve.

Which is inversily proportional to temprature of blackbody

$\lambda_m=\frac{b}{T}$

where b is wein's constant and T is temprature of body

so he observed the wavelength for which he gets peak in blackbody radiation curve and determined the temprature of surface of sun using above formula,

2) so T= 5800K peak wavelength

$\lambda_m=\frac{2.89\times10^{-3}}{5800}$

so,

$\lambda_m=498.27nm$

This is the peak intensity in sunlight spectrum