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Photoelectric emission occurs only when the incident light has more than a certain minimum:

Asked in AIPMT 2011 · Conceptual points of the photoelectric effect

Answer: (4) frequency

Step-by-step solution

Einstein's equation: Kₘₐₓ=h u-h u₀.

An electron can only leave if Kₘₐₓ is positive, which needs h u>h u₀, that is u> u₀.

So there is a minimum frequency, called the threshold frequency, below which no emission occurs however bright the light.

Photoemission is a one-photon-one-electron process, so a photon either has enough energy on its own or it does not; sending more of them does not help.

Why the other options are wrong

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