When a point source of light is at a distance of 50 cm from a photoelectric cell, the stopping voltage is found to be V₀. If the same source is applied at a distance of 1 m from the cell, the stopping voltage will be .

Question

Accepted Answer

(2) V₀. Given: a point source 50 cm from a photocell gives a stopping voltage V₀; the same source is then put at 1 m. Idea: the stopping voltage measures the largest kinetic energy a photoelectron can have, eVₛ = h
u - φ₀. It is settled by the frequency of the light and the work function of the metal. Moving the source further away changes only how many photons arrive each second: the intensity drops by the factor ((0.5)/1)² = 1/4. Each photon still carries the same energy h
u, so the fastest electron still leaves with the same h
u - φ₀. So the stopping voltage is unchanged at V₀; only the photocurrent falls to a quarter.

When a point source of light is at a distance of 50 cm from a photoelectric cell, the stopping voltage is found to be V₀. If the same source is applied at a distance of 1 m from the cell, the stopping voltage will be ______.

Step-by-step solution

Why the other options are wrong