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A certain element 'A' undergoes photoele...

A certain element 'A' undergoes photoelectric effect when bombarded by one photon of indigo light. When the same element was bombarded with two photon of red light no emission took place. Explain the observation.

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Electrons can absorb only one photon at a time. If the photon possesses the required threshold frequency photo emission will take place. Large number of photons of lower frequency will not be able to bring about the photoelectric effect.
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