Question: 38. Which of the following options represent the variation of photoelectric current with property of light shown on the x-axis?
(1) A only
(2) A and C
(3) A and D
(4) B and D
Answer: Option (1)
Explanation:
In the photoelectric effect, the photoelectric current depends on the number of photoelectrons emitted per unit time.
This number is directly proportional to the intensity of incident light,
provided the frequency of light is greater than the threshold frequency.
Graph A shows photoelectric current increasing linearly with the intensity of light.
This is correct because higher intensity means more photons falling per second,
which causes more electrons to be emitted, increasing the current.
Graph B shows photoelectric current independent of intensity of light.
This is incorrect because photoelectric current must increase with intensity.
Graphs C and D show photoelectric current varying with frequency of light.
This is incorrect because photoelectric current does not depend on the frequency of light
(as long as frequency is above threshold); frequency affects the kinetic energy of emitted electrons,
not the current.
Therefore, only graph A correctly represents the variation of photoelectric current with the property of light shown on the x-axis.