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title: "In an experiment, a beam of extremely low-intensity ultraviolet light is directed at a clean zinc plate, and photoelectrons are detected almost instantaneously. In contrast, when a very high-intensity beam of red light is directed at the same plate for a prolonged period, no photoelectrons are emitted. Which of the following statements correctly explains why the photon model of light accounts for these observations, whereas the classical wave model fails?"
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url: "https://nerd-notes.com/ubq/123494/"
date_modified: "2026-09-28T11:59:56+00:00"
---

# In an experiment, a beam of extremely low-intensity ultraviolet light is directed at a clean zinc plate, and photoelectrons are detected almost instantaneously. In contrast, when a very high-intensity beam of red light is directed at the same plate for a prolonged period, no photoelectrons are emitted. Which of the following statements correctly explains why the photon model of light accounts for these observations, whereas the classical wave model fails?

In an experiment, a beam of extremely low-intensity ultraviolet light is directed at a clean zinc plate, and photoelectrons are detected almost instantaneously. In contrast, when a very high-intensity beam of red light is directed at the same plate for a prolonged period, no photoelectrons are emitted. Which of the following statements correctly explains why the photon model of light accounts for these observations, whereas the classical wave model fails?

- **A.** Classical wave theory assumes that the threshold for electron emission is determined strictly by the wave's frequency rather than its amplitude, so high-intensity red light lacks the oscillating electric field strength needed to liberate electrons from the lattice.
- **B.** Classical wave theory predicts that the kinetic energy of emitted electrons depends solely on frequency, whereas the photon model explains that low-intensity beams concentrate total wave energy onto fewer individual electrons.
- **C.** Classical wave theory treats photoelectron emission as a bulk thermal process requiring a substantial time delay for the metal to heat up, whereas the photon model treats light as continuous waves that match atomic spacing.
- **D.** Classical wave theory predicts that energy is distributed continuously along the wavefront, requiring a time delay for an electron to accumulate sufficient energy, whereas the photon model treats light as discrete packets of energy proportional to frequency, enabling instantaneous single-photon interactions.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123494/*