Experimental Setup for Photoelectric Effect
Two conducting electrodes, anode (Q) and cathode (P) are enclosed in an evacuated glass tube as shown in Fig. 5.
- The battery or other source of potential difference creates an electric field in the direction from anode to cathode.
- Light of certain wavelength or frequency falling on the surface of cathode causes a current in the external circuit called photoelectric current.
- As potential difference increases, photo electric current also increases till saturation is reached.
- When polarity of battery is reversed (i.e., plate Q is at negative potential w.r.t. plate P) electrons start moving back towards the cathode.
- At a particular negative potential of plate Q no electron will reach the plate Q and the current will become zero, this negative potential is called stopping potential denoted by V0. Maximum kinetic energy of photo electrons in terms of stopping potential will therefore be .