Question:medium

Light of frequency two times the threshold frequency is incident on photosensitive material. If the incident frequency is made 1/3 rd and intensity is doubled, then the photoelectric current will

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Photoelectric current depends on the intensity of light ONLY IF the incident frequency is above the threshold frequency. If $\nu < \nu_0$, the current is always zero, no matter how intense the light is.
Updated On: Jun 1, 2026
  • increase
  • decrease
  • be zero
  • be halved
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The Correct Option is C

Solution and Explanation

Step 1: Note the starting frequency.
The light begins at $\nu = 2\nu_0$, which is above the threshold $\nu_0$, so electrons come out at first.

Step 2: Find the new frequency.
The frequency is cut to one third: $\nu' = \tfrac13(2\nu_0) = \tfrac{2}{3}\nu_0$.

Step 3: Compare with threshold.
Now $\tfrac{2}{3}\nu_0$ is less than $\nu_0$, so the light no longer has enough energy per photon to free any electron.

Step 4: Effect of intensity.
Doubling intensity only adds more photons, but each is still too weak, so no current flows. \[ \boxed{\text{The current will be zero}} \]
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