Exam-style question
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Explain why wave theory cannot account for the photoelectric effect.
Model answer
What a good answer should say
- Wave theory suggests that light energy is distributed continuously, which would imply that increasing light intensity should increase the energy of emitted electrons.
- However, experiments show that electrons are emitted only when light exceeds a certain threshold frequency, regardless of intensity.
- This indicates that light consists of discrete packets of energy (photons), which contradicts wave theory.
Explanation
Why this works
This answer is strong because it clearly identifies the cause (wave theory's continuous energy distribution), explains the mechanism (the implication of intensity affecting energy), and states the effect (threshold frequency requirement) along with its consequence (discreteness of light energy). The question tests understanding of the limitations of classical wave theory in explaining quantum phenomena.
Common mistake
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