2.10 Explain why the existence of photons (quantized light energy) explains the photoelectric effect.

Why does the existence of photons (quantized light energy) explain the photoelectric effect?

• Photons are discrete packets of energy. For the photoelectric effect, each photon must have enough energy to overcome the work function (the energy needed to release electrons from the metal).

• The photoelectric effect shows that light doesn’t transfer energy continuously, but rather in discrete units (photons).

• Threshold frequency: Below a certain frequency (threshold frequency), no electrons are ejected, no matter how intense the light is, because individual photons don’t have enough energy to eject electrons.

• Once the frequency exceeds the threshold, photons with higher energy cause electrons to be ejected. The number of electrons increases with light intensity because more photons hit the metal, but their energy is still tied to the frequency.

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