Q111 / 120 · VITEEE 2014 · Physics

If the distance of $100 \mathrm{~W}$ lamp is increased from a photocell, the saturation current $\mathrm{i}$ in the photocell varies with the distance $d$ as

  • A
    $\mathrm{i} \propto \mathrm{d}^{2}$
  • B
    $i \propto d$
  • C
    $\mathrm{i} \propto \frac{1}{d}$
  • Correct answer
    D
    $\mathrm{i} \propto \frac{1}{d^{2}}$

Solution

As we know, Photoelectric current depends on the intensity of incident radiation i.e., $i \propto I$ But, intensity of radiation $I \propto \frac{1}{d^{2}}$ so, $i \propto \frac{1}{d^{2}}$

Hence, the correct answer is option: 'D'.

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