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When Dr. Lavelle was lecturing last week on the photoelectric effect, I was a little confused on the distinction between the frequency and amplitude of a wave. I know that frequency is the number of wave cycles per second, and that amplitude is the height of a wave, but which of these two contributes to the intensity of the wave? Which one is more important when we are discussing the photoelectric effect: amplitude or frequency?
Amplitude contributes to the intensity of a wave. Thus amplitude has no contribution to the photoelectric effect because of its relation to intensity. Frequency is most important to the photoelectric effect.
Neither of these has an effect on the intensity of light. If light acted as a classical wave, then the amplitude (energy) of the wave would be proportional to its intensity. The results of the photoelectric experiment, however, showed that light doesn't always act as a classical wave since increasing the intensity didn't eject electrons for low frequency light. The conclusion was that light also had particle-like properties (photons), where the intensity of light is proportional to the number of photons and not the amplitude of the wave. Increasing the intensity of light would result in more electrons being ejected, but only if each photon has enough energy to eject an electron (high frequency / short wavelength).
Amplitude does not have an effect on the intensity of the wave. Frequency, however, does have an effect on the intensity of the wave and is more important for the photoelectric effect. Frequency relates to the number of photons and the energy within each of these photons. An increased frequency can eject more electrons from the metal in the photoelectric effect.
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