Quantum mechanicsLesson 1 of 2 in the course Photons and Matter Waves

Photoelectric Effect: Photons, Thresholds, and Stopping Potential

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces the photoelectric effect and the apparatus used to investigate it. Understanding the setup makes it possible to interpret how light can eject electrons and how experiments measure their behavior.

The photoelectric effect occurs when electromagnetic radiation of sufficiently high frequency strikes a metal surface and causes electrons to leave it. The emitted electrons are called photoelectrons. The incoming radiation is often monochromatic, meaning it has one frequency, or equivalently one wavelength.

All flashcards

What is the work function of a metal?
The minimum energy needed to release an electron from the metal.
What is a photon?
A quantum of electromagnetic radiation with energy Ef=hfE_f=hf.
What is the cutoff wavelength?
The longest wavelength that can eject electrons from a particular material.
What is saturation current in a photoelectric experiment?
The current reached when the anode collects all emitted photoelectrons.
How does stopping potential relate to maximum kinetic energy?
The stopping potential gives the maximum kinetic energy: Kmax=eΔVsK_{max}=e\Delta V_s.

Quiz questions

  1. At fixed light frequency, what happens to maximum photoelectron kinetic energy when light intensity increases?Answer: It stays the same because photon energy is unchanged.
  2. In the photon model of photoemission, how does a photon transfer energy to an electron?Answer: It transfers its energy in a single, complete interaction.
  3. Why is prompt photoemission surprising in the classical continuous-wave picture?Answer: That picture suggests an electron should need time to accumulate enough energy.
  4. Why does increasing light intensity generally increase photocurrent?Answer: More photons arrive per unit time, allowing more electrons to be emitted.
  5. What does the slope of a graph of KmaxK_{max} versus frequency represent?Answer: Planck's constant.

Based on University Physics Volume 3 by Samuel J. Ling, Jeff Sanny, William Moebs (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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