(i) In the explanation of photo electric effect, we assume one photon of frequency v collides with an electron and transfers its energy. This leads to the equation for the maximum energy E max of the emitted electron as where ϕ 0 is the work function of the metal. If an electron absorbs 2 photons (each of frequency v) what will be the maximum energy for the emitted electron? (ii) Why is this fact (two photon absorption) not taken into consideration in our discussion of the stopping potential?