Photoelectric effect
The phenomenon in which electrons are emitted from a material when light of sufficiently high frequency shines on it. The kinetic energy of emitted photoelectrons depends on the light's frequency, not its intensity, contradicting the classical wave model. This effect demonstrates the particle nature of light (photons) and supports the photon model of electromagnetic radiation.
Formula
½mv²_max = hf − φ (where φ = hf₀ is the work function)
Real World
Solar panels on the International Space Station rely on the photoelectric effect: photons from sunlight eject electrons in silicon cells, and engineers select materials with work functions matched to peak solar frequencies to maximise efficiency.
Exam Focus
When 'explain' is the command word, state: one photon absorbed by one electron, energy must exceed work function, excess becomes kinetic energy — all three points are needed for full marks.
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