question_answer

                A photo-cell employs photoelectric effect to convert:                                                                   

A)                  change in the frequency of light into a change in electric voltage

B)                  change in the intensity of illumination into change in photoelectric current

C)                  change in the intensity of illumination into a change in the work function of the photocathode

D)                  change in the frequency of light into a change in the electric current

Correct Answer: B

Solution :

                In a photoelectric effect when monochromatic radiations of suitable frequency fall on the photo-sensitive plate called cathode, the photoelectrons are emitted which get accelerated towards anode. These electrons flow in the outer circuit resulting in the photoelectric current.                 Using the incident radiations of a fixed frequency, it is found that the photoelectric current increases linearly with the intensity of incident light as shown in figure. Hence, a photocell employs photo­electric effect to convert change in the intensity of illumination into a change in photo­electric current.