# The anode voltage of a photocell is kept fixed. The wavelength $\lambda$ of the light falling on the cathode is gradually changed. The plate current vs. $\lambda$ curve is

Ans : (d)
According to the photoelectric effect in a photocell, if a light of wavelength $\lambda$
is incident on a cathode, and then electrons are emitted, which constitute the
photoelectric current. Photocell is based on the principle of photoelectric effect.
As the wavelength of light changes, there is no change in the number of
electrons emitted and hence, no charge in current. Thus the wavelength of
incident light and plate current are independent to each other.
Plate current depends on intensity of light used.

edited Mar 13, 2014