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Learning Goal

Part of: The Quantum Nature of Light — 2 of 3 chapter items

Einstein and the Photoelectric Effect

21.2

"When light strikes certain materials, it can eject electrons from them. This is called the **photoelectric effect**, meaning that light (*photo*) produces electricity." "In fact, the EM wave itself is actually composed of tiny quantum packets of energy called **photons**." "The kinetic energy KE of an ejected electron equals the photon energy minus the binding energy BE of the electron in the specific material." "$$KE_e = hf - BE,$$ where $KE_e$ is the maximum kinetic energy of the ejected electron, $hf$ is the photon's energy, and BE is the binding energy of the electron to the particular material. The binding energy is also often called the work function of the material."

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"When light strikes certain materials, it can eject electrons from them. This is called the photoelectric effect, meaning that light (photo) produces electricity."
"In fact, the EM wave itself is actually composed of tiny quantum packets of energy called photons."
"The kinetic energy KE of an ejected electron equals the photon energy minus the binding energy BE of the electron in the specific material."
"$$KE_e = hf - BE,$$ where $KE_e$ is the maximum kinetic energy of the ejected electron, $hf$ is the photon's energy, and BE is the binding energy of the electron to the particular material. The binding energy is also often called the work function of the material."

What you'll learn

  1. Describe the photoelectric effect and Einstein's explanation of it in terms of photons
  2. Explain why the photoelectric effect cannot be explained by the classical wave model
  3. Use E = hf and KE_e = hf − BE to calculate photon energy and the maximum kinetic energy of an ejected photoelectron
  4. Relate binding energy (work function) and threshold frequency via BE = hf₀
  5. Describe technological applications of the photoelectric effect (electric eyes, photocells, movie soundtracks, solar cells)

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