Ordinary bodies $P$ and $Q$ radiate maximum energy with a wavelength difference of $3 \mu m$. The absolute temperature of body $P$ is four times that of $Q$. The wavelength at which body $Q$ radiates maximum energy is (in $\mu m$)

Wien's displacement law expresses the relation between:

$A$ star which appears blue will be

The intensity of radiation emitted by the sun has its maximum value at a wavelength of $510\;nm$ and that emitted by the north star has the maximum value at $350\;nm$. If these stars behave like black bodies,then the ratio of the surface temperature of the sun and north star is

The colour of a star is an indication of its

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