Black-body radiation

$E=\sigma T^4$, Stefan-Boltzman Law. $\sigma =5.67\cdot {10}^8$. $U(\nu ,T)=A{\nu }^3\exp (-\beta \nu /T)$

Oscillators $\nu$ are quantized by energy such that $E=n\hslash \nu$, $n\in \mathbb{N}$.

• $U(\nu ,T)=\frac{8\pi {\nu }^2}{c^3}\frac{\hslash \nu }{\exp (\hslash \nu /(k_{B}T))-1}$