Describe the experimental study of the photoelectric effect with a labelled diagram. Draw graphs to show the effect of intensity and of frequency on the photocurrent, and state the conclusions.

1. 1 · Give the aim in one line. To study how photocurrent depends on intensity, collector potential and frequency.
2. 2 · Draw the apparatus. [Evacuated tube with emitter C and collector A; quartz window with light falling on C; battery with potential divider and commutator; voltmeter across C and A; microammeter in series]
3. 3 · Effect of intensity. Photocurrent ∝ intensity; the graph is a straight line through the origin.
4. 4 · Effect of potential. The current rises to saturation. With A negative, it falls to zero at −V₀, and eV₀ = K_max.
5. 5 · Draw the current-potential graphs. [Two intensities: same −V₀, different saturation currents. Three frequencies: different −V₀, same saturation current]
6. 6 · Effect of frequency. V₀ increases linearly with ν; there is no emission below ν₀.
7. 7 · Real life. Light sensors give more current in brighter light.
8. 8 · Close in one line. So, intensity controls the number of electrons, and frequency controls their maximum energy.

Scoring tip: Draw the graphs with labelled axes and mark −V₀ and the saturation current; they carry most of the marks.