In the explanation of photo electric effect , we assume one photon of frequency $\alpha$ collide with an electron and transfer its energy . This leads to the equation for the maximum energy $E_{max}$ of the emitted electron as $ E_{max}= h \alpha - \phi _0$ where $ \phi _0$ is the work function of the metal. If an electron absorbs 2 photons (each of frequency ) what will be the maximum energy for the emitted electron ?
