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The Photoelectric Effect

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Estimated time: 3 minutes
Maharashtra State Board: Class 11

Definition: Photoelectric Effect

The phenomenon of emission of electrons from a metal surface, when radiation of appropriate frequency is incident on it, is called the Photoelectric Effect.

CBSE: Class 12
Maharashtra State Board: Class 11

Key Points: Photoelectric Effect

  • When light of frequency ≥ threshold frequency (ν₀) falls on a metal surface, electrons are emitted.
  • If ν < ν₀ → no emission, regardless of intensity.
  • The threshold frequency (ν₀) varies with metal.
  • Energy equation: \[h\nu=h\nu_0+\frac{1}{2}mv^2\]
  • Maximum kinetic energy depends only on frequency, not on intensity.
  • Number of emitted electrons depends on intensity (for ν ≥ ν₀).
  • Emission of electrons is instantaneous (no time lag).
  • Increasing frequency increases the kinetic energy of electrons.
  • Increasing intensity increases the number of electrons, not their energy.
  • The photoelectric effect proves the particle (quantum) nature of light.
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