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11. Dual nature of radiation and matter — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics11. Dual nature of radiation and matter1 Mark
MCQ
A photocell is illuminated by a small bright source placed $d\; m$ away. When the same source of light is placed $\frac{d}{2}\;m$ 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 $4$
d
(d) Number of photoelectrons $\propto$ $\frac{1}{{{{({\rm{Distance}})}^2}}}$.

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