Which classical theory was contradicted by experiments with the photoelectric effect?

• A. The kinetic molecular theory
• B. The quantum theory of light
• C. The wave theory of light
• D. The atomic theory of matter

Answer: (C)

Verified step by step guidance

1. Understand the context of the photoelectric effect: it involves the emission of electrons from a metal surface when light shines on it.
2. Recall that before the photoelectric effect was explained, light was widely considered to behave purely as a wave, according to the classical wave theory of light.
3. Recognize that the classical wave theory predicted that the energy of emitted electrons should depend on the intensity of light, not its frequency, and that there should be a time delay before electrons are emitted.
4. Note that experiments showed electrons are emitted immediately and only if the light frequency is above a certain threshold, regardless of intensity, which contradicts the classical wave theory.
5. Conclude that these experimental results contradicted the classical wave theory of light and supported the quantum theory of light, which treats light as particles called photons.