The work functions of Caesium (Cs), Potassium (K) and Sodium ( Na ) are 2.14 eV, 2.30 eV and 2.75 eV

Question

The work functions of Caesium (Cs), Potassium (K) and Sodium ( Na ) are 2.14 eV, 2.30 eV and 2.75 eV respectively. If incident electromagnetic radiation has an incident energy of 2.20 eV , which of these photosensitive surface may emit photoelectrons?\

Professor PC Thomas Classes · Answer

(c) : $W_{\mathrm{Cs}}=2.14 \mathrm{eV}, W_{\mathrm{K}}=2.30 \mathrm{eV}, W_{\mathrm{Na}}=2.75 \mathrm{eV}$\ $E=2.20 \mathrm{eV}$.\ Electrons are emitted only when the incident energy is more than work function.\ So, $W_{\mathrm{Cs}}>E$, so option (c) is correct.\