The electron and hole concentration in an extrinsic semiconductor in thermal equilibrium is given by:

Where $n_e$ = electron density
$n_h$ = hole density
$n_i$ = intrinsic charge density

$n_e . n_h=n_i^2$

The correct answer is Option (1) → $n_e . n_h=n_i^2$

Electron-hole concentration in Thermal equilibrium is given by $n_e n_h=n_i^2$