Question

A photo cell is receiving light from a source placed at a distance of 1 m. If the same source is to be placed at a distance of 2 m, 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 $\propto \left(Intensity\right)\propto \frac{1}{(Distance{)}^2}$
Therefore an increment of distance two times will reduce the number of ejected electrons to $\frac{1}{4}th$ of the previous one.