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Why does light need both wave and particle models?
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When white light is spread apart by a prism or a diffraction grating, the colours of the visible spectrum appear. The colours vary according to their wavelengths. Violet has the highest frequencies and shortest wavelengths, and red has the lowest frequencies and the longest wavelengths.
Light requires both wave and particle models because neither classical framework can fully explain its behavior on its own. This phenomenon is known as wave-particle duality.123
- Wave Model: This model is necessary to explain phenomena such as interference and diffraction, where light waves overlap to create patterns of reinforcement or cancellation, as demonstrated in Youngâs experiment.24
- Particle Model: This model is required to explain interactions where light behaves as discrete packets of energy, or photons. For example, the photoelectric effectâwhere light dislodges electrons from a metal surfaceâcannot be explained by wave theory, as the energy of the ejected electrons depends on the light's frequency rather than its intensity.15
Ultimately, quantum mechanics reveals that these classical models are merely complementary, approximate descriptions of an underlying reality that neither model can capture entirely.2