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Electron, Photon, Photo-electric Effect and X-Rays — JEE physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceJEE physicsElectron, Photon, Photo-electric Effect and X-Rays1 Mark
MCQ
A photocell is illuminated by a small bright source placed $1 m$ away. When the same source of light is placed $\frac{1}{2} m$ away, the number of electrons emitted by photo cathode would
  • A
    Decrease by a factor of $2$
  • B
    Increase by a factor of $2$
  • C
    Decrease by a factor of $4$
  • ✓
    Increase by a factor of $4$
✓

Answer

Correct option: D.
Increase by a factor of $4$
Number of photoelectrons $\propto \frac{1}{(\text { Distance })^2}$.

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