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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 intensity is doubled?

1. four times
2. one-fourth
3. zero
4. doubled

Correct answer: zero

Solution

The photoelectric current depends on the intensity of light, but the emission of photoelectrons requires the frequency to be above the threshold frequency. Halving the frequency makes it less than the threshold frequency, so no photoelectrons are emitted, and the current becomes zero.

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