dual nature of matter & radiation

Light of frequency 1.5 times the threshold frequency is incident on photo-sensitive material.If the frequency is halved & intensity is doubled,the photo current becomes
1. Quadrupled
2. Doubled
3. Halved
4. Zero

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asked by hriday
  1. Actually, it will depend upon how the quantum efficiency of the photosensitive material varies with frequency. The "quantum efficiency" almost always depends upon wavelength (and therefore frequency), especially near the threshold for the photelectric effect.

    In this case, you have a kind of trick question, and an easy answer. Since you halve the frequency and you started out at 1.5 times the threshold frequency, you end up below (at 3/4 of) the threshold frequency for photoelectron emission, and the photocurrent is ZERO.

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    posted by drwls

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