Describe an experiment to study the photoelectric effect. Explain the terms saturation current and stopping potential.

How to lay out the answer. Follow the frame, then write it in your own words.

1 · Define the effect. Emission of electrons from a metal when light of frequency above a threshold falls on it.
2 · Describe the set-up. Photocathode C and collector A in an evacuated tube with a quartz window; battery with a commutator; microammeter in series.
3 · Draw the apparatus. [Diagram: evacuated tube, quartz window, light on C, plate A, battery with commutator, microammeter]
4 · Explain saturation current. With A positive, the current rises to a constant value when all emitted electrons are collected.
5 · Explain stopping potential. With A negative, the current falls to zero at V₀, where eV₀ = ½mv²max.
6 · Close in one line. So, intensity controls the current, and frequency controls the stopping potential.

Scoring tip: Draw the circuit carefully with the commutator and microammeter. Write eV₀ = ½mv²max as a formula, not only in words.