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Question
Is it always possible to see the photoelectric effect with a red light?
Solution
No, it is not possible to see the photoelectric effect with a red light.
Explanation:
The energy required to rip an electron out of its orbital is equal to the electron's work function, and photons in red light lack this energy. Because light behaves like particles rather than a continuous stream, even very high-intensity red light will never be able to overcome an electron's work function (in this case), because each photon fails to do so. This demonstrates the particle behaviour of light. The photoelectric effect demonstrates the particle nature of light, and even very intense or prolonged exposure to red light will not cause the effect if the photon energy is insufficient.
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