Physics Question on Dual nature of radiation and matter

Question

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

Answer 1

Solution

The correct option is (B): The minimum energy required for a photoelectron to escape from a metal surface is given by its work function. If the energy of the incident photon is greater than the work function of the metal, then photoelectrons will be emitted.

For the given incident energy of 2.20eV, only Caesium (Cs) can emit photoelectrons because its work function (2.14 eV) is less than the incident energy. The work functions of Potassium (K) and Sodium (Na) are greater than the incident energy, so they cannot emit photoelectrons under these conditions.