The energy of a photon of sodium light `( lamda = 589 nm)` equal to the band gap of a semiconducing material .
Find the value of E /kT at a temperature of 300 K.

Explanation

At T= 300 K, KT=(`8.62 xx 10^(-5) eV//K`) (300K)
= 25.86 `xx 10^(-3) ` eV.
Thus`(E )/( kT ) = ( 2.1 eV )/( 25.86 xx 10^(-3)) = 81`
The available thermal energy is nearly 81 times less than that of the required energy to create electron hole pair. So it is difficult for the thermal energy to create the hole-electron pair but a photon of light can do it easily.