Question

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

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

Answer 1

Answer: (D)

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