AP Physics 2 / Unit 15: Modern Physics
15.5 The Photoelectric Effect
Notes
Light ejects electrons from a metal only if each photon has enough energy: $K_{max}=hf-\phi$ ($\phi$ = work function).
- Brighter light gives more electrons, not faster ones.
- Below the threshold frequency, no electrons are emitted.
Practice
Increasing light intensity (above threshold) increases:
More photons.
$hf=5$ eV, $\phi=2$ eV. $K_{max}=$
$5-2$.
The photoelectric effect is evidence that light:
Energy depends on frequency.
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