Question

A photocell is receiving light from a source placed at a distance of $1m$. If the same source is to be placed at a distance of $2m$, then the ejected electron

• A. Moves with one - fourth energy as that of the initial energy
• B. Moves with one-fourth of momentum as that of the initial momentum
• C. Will be half in number
• D. Will be one - fourth in number

Answer 1

The correct option is D Will be one - fourth in number

Number of ejected electrons is inversely proportional to square of distance between source and photocell.

So, $n\propto \frac{1}{d^2}$

$\Rightarrow \frac{n_1}{n_2}=(\frac{d_2}{d_1}{)}^2$

$\frac{n_1}{n_2}=(\frac{2}{1}{)}^2$

$n_2=\frac{n_1}{4}$

So, one - fourth electrons will eject.