Week7 - But does light always behave like a wave ? The...

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But does light always behave like a wave ?
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The Photoelectric effect When light is incident on a metal surface, electrons can be ejected and give rise to a photoelectric current. Collector plate can be held at negative voltages to repel photoelectrons. Minimum required voltage to stop all current is called the stopping or retarding voltage - a measure of the e - ’s Kinetic Energy
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Specific predictions from the Wave Theory of Light : 1. Larger Intensity of light gives larger current 2. For weaker intensities, there can be a time lag between illumination and photoelectron emission, as electrons slowly accumulate energy from incoming light waves.
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However, experiments contradict these predictions! 1. There was never any lag time. 2. Increasing intensity of incident light may increase the # photo- electrons but not their KE or stopping voltage.
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f of incident light changes, so does the stopping potential V o . V o ~ f 4. Red light never produced any photoelectrons, no matter what the intensity. 5. Violet light, even at low
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Week7 - But does light always behave like a wave ? The...

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