A freshly polished sodium surface is illuminated with monochromatic radiation of…
PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation
Problem
A freshly polished sodium surface is illuminated with monochromatic radiation of frequency much higher than its threshold frequency. The variation of photocurrent with the applied collector potential is recorded at two different light intensities, keeping the frequency unchanged.
(i) Define saturation photocurrent for a photoelectric cell.
(ii) Explain, on the basis of the photon–electron interaction, why the saturation photocurrent is directly proportional to the incident light intensity whereas the stopping potential remains unaltered when the intensity alone is varied.
(iii) If the incident intensity is increased to four times its initial value, describe qualitatively how the photocurrent–voltage characteristic curve will be modified. Sketch the two curves on the same axes and mark clearly the changes in saturation region and stopping potential region.