Which of the following best describes Einstein's explanation of the photoelectric effect?

• A. Light behaves purely as a wave, and the energy of ejected electrons depends solely on the amplitude of the light wave.
• B. Electrons are emitted from a metal surface when the temperature of the metal is increased by incident light.
• C. Electrons are emitted from a metal surface only when the intensity of light is high enough, regardless of the light's frequency.
• D. Light consists of discrete packets of energy called photons, and electrons are ejected from a metal surface when the energy of a photon exceeds the work function of the metal.

Answer: (D)

Verified step by step guidance

1. Understand the photoelectric effect: it involves the emission of electrons from a metal surface when light shines on it.
2. Recall that classical wave theory predicted that the energy of ejected electrons should depend on the light's intensity (amplitude), but experiments showed this was not the case.
3. Einstein proposed that light is quantized into discrete packets of energy called photons, each with energy given by the equation \(E = h \nu\), where \(h\) is Planck's constant and \(\nu\) is the frequency of light.
4. According to Einstein, electrons are emitted only if the energy of an individual photon exceeds the metal's work function \(\phi\), which is the minimum energy needed to eject an electron.
5. Therefore, the key point is that the frequency (and thus photon energy), not the intensity, determines whether electrons are emitted, explaining the photoelectric effect accurately.