• Tags: photoelectric, practical, setup
• Difficulty: Moderate

The experimental setup consists of a photosensitive cathode and a collecting anode in an evacuated tube. When light shines on the cathode, electrons are emitted and travel to the anode, creating a current. A retarding potential (negative on anode) is applied to measure $V_{0}$.

Important practical points for JEE: (1) Saturation current = ne (n = electrons emitted per second = number of photons absorbed per second × quantum efficiency). (2) Even at zero applied potential, some current flows because electrons have initial KE. (3) At V = -$V_{0}$, even the most energetic electrons are stopped. (4) If the frequency is below threshold, no current flows even with forward bias. (5) The work function can differ for different crystal faces of the same metal. (6) Temperature effects: higher temperature slightly reduces the effective work function.