Question

What is the energy of photon of wavelength 1 mm? Compare this with the characteristic thermal energy at 3000K.​

Answer 1

$E=h\nu=\frac{hc}{\lambda}=\frac{6.626\cdot10^{-34}\cdot3\cdot10^8}{1\cdot10^{-3}}=19.878\cdot10^{-23}(J)$

The characteristic thermal energy

$E_t\approx kT=1.38\cdot10^{-23}\cdot3000=4.14\cdot10^{-20}(J)$

$E_t/E\approx208$

So, the characteristic thermal energy is 208 times greater than the energy of photon. Answer