Photoelectric Effect

Syllabus tag: KCSE | Physics | Form 4 | Topic 38 Photoelectric Effect

Lesson objectives

By the end of this topic, you should be able to:

• Explain the photoelectric effect and define work function and threshold frequency.
• State Einstein's photoelectric equation and apply it.
• Explain the observations that the wave theory cannot account for.
• Describe photoelectric devices and their applications.

Summary

The photoelectric effect is the emission of electrons from a metal surface when light of sufficiently high frequency falls on it. Emission occurs only above a threshold frequency, whatever the intensity. Einstein's equation is hf = W₀ + ½mv²max, and it establishes that light behaves as photons — packets of energy.