Module 5 : MODERN PHYSICS
Lecture 23 : Black Body Radiation
  Example 5
  The exercise above shows that the sun emits mostly in the visible region. Compare the total intensity of radiation emitted by a star of similar size as the sun whose surface temperature is 7200 K.
Solution
 
The total intensity is given by Stefan's law,
 
$\displaystyle \frac{T_{star}^4}{T_{sun}^4} = \left(\frac{7200}{6000}\right)^4 = 2.07$
 
However, the star emits its peak intensity in the blue end of the spectrum as the wavelength at which the radiation intensity being inversely proportional to the temperature is given by
 
$\displaystyle \lambda_{max} = \frac{0.29}{7200} = 4.02\times 10^{-5}\ \ {\rm cm} \approx 402\ \ {\rm nm}$

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