Observations of Photoelectric Effect

Observations of Photoelectric Effect 

1. Existence of threshold frequency

  • For a given metal, no photoelectrons are emitted if the frequency of the incident light is lower than a certain frequency. If the light frequency is below this threshold frequency for that metal, no photoelectrons can be emitted, no matter the intensity of the incident radiation is or for how long it falls on the surface of the metal.

2. Emission is instantaneous

  • Emission of photoelectrons takes place almost instantaneously after the light shines on the metal, with no detectable time delay. It does not depend on the intensity of the incident radiation.

3. Maximum Kinetic Energy of the photoelectron is independent of intensity of incident electromagnetic radiation

  • Photoelectrons emitted from a metal have a range of velocities from zero up to a maximum $V_{max}$. The maximum kinetic energy $\frac{1}{2} m V_{max}^{2}$ was found to depend linearly on the frequency of the radiation and is independent of its intensity.

4. Rate of emission of photoelectrons proportional to intensity of incident electromagnetic radiation

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