Why does red light not cause the ejection of electons no matter what the intensity Related: Wave-Particle Duality - Quantum Mechanics, CSIR-NET Physical Sciences?

Question

Why does red light not cause the ejection of electons no matter what the intensity Related:  Wave-Particle Duality - Quantum Mechanics, CSIR-NET Physical Sciences?

Answer

To eject electrons from a metal surface,there should be a threshold frequency below which no matter how much the intensity is,the electrons cannot be ejected because E=h*v where v is frequency of EM wave.So energy is related to frequency not the intensity (as we know red light is the  lowest frequency EM wave in the Visible spectrum so its frequency is not enough to eject electrons) .The intensity is related to photo current, that means the frequency is above the threshold frequency, and you increase the intensity,More electrons will be ejected at the same time hence more photo current .But below threshold frequency  the intensity(alone) cannot eject electrons.

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