The black body photons represent a system of the 3-dimensional standing waves, the nodes of which contain the material particles. Since each particle emits one photon, the number of photons is the number of standing waves ("Waves", 7) multiplied by 2, because an electromagnetic wave may consist of two orthogonal waves (circular polarization). The spectral density of energy per volume unit of the body is expressed by the average photon energy ("Quantum mechanics", 6): $u(\omega,T)=2\frac{\mathrm{d}n}{\mathrm{d}\omega}\epsilon(\omega)=2\frac{\omega^2}{2\pi^2c^3}\frac{\hbar\omega}{\exp(\hbar\omega/kT)-1}\tag{1}$ $u(\lambda,T)=2\frac{\mathrm{d}n}{\mathrm{d}\lambda}\epsilon(\lambda)=2\frac{4\pi}{\lambda^4}\frac{hc/\lambda}{\exp(hc/\lambda kT)-1}\tag{2}$ The luminous intensity $$I$$ is a radiation power per steradian: $I=\frac{c}{4\pi}u$ The radiation power per area unit of the body surface, according to Lambert's cosine, law is: $f=\pi I=\frac{c}{4}u$ As a result, the spectral density of power per area unit of the black body surface is expressed by well-known Planck’s law: $u(\omega,T)=\frac{\hbar\omega^3}{4\pi^2c^2}\frac{1}{\exp(\hbar\omega/kT)-1}\tag{3}$ $u(\lambda,T)=\frac{2\pi\hbar c^2}{\lambda^5}\frac{1}{\exp(\hbar c/\lambda kT)-1}\tag{4}$ Wien's displacement law is produced by finding the extremum of (4). According to it, as the bodies temperature grows, their own glow color becomes red, orange, yellow and white. The thermal radiation is mainly focused into the infrared and visible ranges. $\lambda_{max}=\frac{b}{T}\;\;\;\;\;b\approx 0,003\;m\cdot K\tag{5}$ Stefan–Boltzmann law is a power, which is radiated by the area unit: $P=\int_0^{\infty}{f(\omega,T)\mathrm{d}\omega}=\frac{\pi^2k^4}{60c^2\hbar^3}=\sigma T^4\tag{6}$