Q. 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
Explanation
(d) Number of ejected electrons $\propto$ (Intensity) $\propto \frac{1}{(Distance)^{2}}$
Therefore an increment of distance two times will reduce the number of ejected electrons to $\frac{1}{4}th$ of the initial value
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.