Here $h$ is the <Planck constant>, $\nu$ is the radiation <frequency>, $c$ is the <speed of light> in vacuum, $k_B$ is the <Boltzmann constant>, and $T$ is the absolute <temperature> in <kelvin>. The quantity $U_\nu$ is spectral <energy density> per unit <frequency>, so $U_\nu\,d\nu$ is <energy> per unit <volume> in the interval $[\nu,\nu+d\nu]$, and $h\nu/(k_BT)$ is dimensionless.

Solution

Past exam of the short options paper of the physics Prelims of the University of Oxford / 2021 / S03 / 1 / b / Solution

 Solution (source code)