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Photoelectric Effect - A Level Physics Definition

Reviewed by: Leander Oates

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What is photoelectric effect?

In A Level Physics, the photoelectric effect is the phenomenon in which electrons are emitted from the surface of a metal upon the absorption of electromagnetic radiation.

Only light of a frequency above a certain threshold (called the threshold frequency) can cause photoelectric emission, regardless of its intensity. The energy of the emitted photoelectrons is directly proportional to the frequency of the incident light.

The photoelectric equation is:

h f space equals space capital phi space plus space E subscript k space m a x end subscript

Where:

  • h = Planck's constant, measured in joule seconds (straight J space straight s)

  • f = the frequency of the incident radiation, measured in hertz (Hz)

  • capital phi (the Greek letter phi) = the work function of the material, measured in joules (straight J)

  • E subscript k space m a x end subscript = the maximum kinetic energy of the photoelectrons, measured in joules (straight J)

  • h f is equal to the energy carried by a single photon at the given frequency f

The photoelectric effect provided crucial evidence for the quantum theory of light, challenging classical wave theories and contributing to the development of modern quantum mechanics.

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Leander Oates

Reviewer: Leander Oates

Expertise: Senior Physics Content Creator

Leander graduated with First-class honours in Science and Education from Sheffield Hallam University. She won the prestigious Lord Robert Winston Solomon Lipson Prize in recognition of her dedication to science and teaching excellence. After teaching and tutoring both science and maths students, Leander now brings this passion for helping young people reach their potential to her work at SME.

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