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Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. What will be the photoelectric current if the frequency is halved and the intensity is doubled?

Asked in NEET 2020 · Conceptual points of the photoelectric effect

Answer: (3) zero

Step-by-step solution

The incident frequency is u=1.5 u₀, comfortably above the threshold, so emission does happen to begin with.

Halving it: u'=(1.5 u₀)/2=0.75 u₀.

Now 0.75 u₀< u₀, so each photon carries less than the work function and cannot free an electron.

Doubling the intensity sends twice as many photons per second, but photoemission is a one-photon-one-electron process, so two weak photons do not combine to free one electron.

The photoelectric current is therefore zero.

Why the other options are wrong

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