The black body spectrum of an object $O _1$ is such that its radiant intensity (i.e. intensity per unit wavelength interval) is maximum at a wavelength of $200\,nm$. Another object $O _2$ has the maximum radiant intensity at $600\,nm$. The ratio of power emitted per unit area by source $O _1$ to that of source $O _2$ is
AIIMS 2015, Medium
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(d)
The wavelength of peak of blackbody spectrum is related to the temperature by:
$\lambda_{\max } T = k$
where $k$ is a constant.
Hence $\lambda_1 T_1=k$
and $\lambda_2 T _2= k$
Power emitted per unit area $\propto T ^4$
Therefore $\frac{ I _1}{ I _2}=\frac{ T _1^4}{ T _2^4}=\frac{\lambda_2^4}{\lambda_1^4}=81$
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