Photoelectric Effect

The emitted electrons are called: photoelectrons. Important experimental observations include: Below a certain frequency: **f < f₀ no photoelectrons are emitted, regardless of increasing light intensity. `f₀` is the threshold frequency**.

Above threshold, increasing frequency increases the maximum kinetic energy of emitted electrons.

At fixed frequency above threshold, greater intensity generally increases the number/rate of emitted photoelectrons. It does **not** by itself increase the maximum kinetic energy.

Photoelectric emission occurs without the long delay expected from a simple classical continuous-energy model. These observations support photon theory.

Threshold: **hf₀ = φ** where `φ` is work function. Full equation comes in next topic.