Question

Consider the two following A and B and identify the correct choice given in the answers.
a. In the photovoltaic cells the photoelectric current produced is not proportional to the intensity of incident light.
b. In gas filled photo emissive cells, the velocity of photoelectrons depends on the wavelength of the incident radiation.
A. Both A and B are true
B. Both A and B are false
C. A is true but B is false
D. A is false but B is true

Answer 1

Hint: When photons are incident on the photovoltaic cells the electron in the valence cell of the metal gets ejected by overcoming the valence energy of the cell of the metal atom. The flow of photoelectrons constitutes photoelectric current.

Complete step by step solution:
As we know that the flow of charge constitutes the electric current, similarly the current due to the flow of the photoelectrons is called the photoelectric current. The photoelectric current is proportional to the rate of flow of the photoelectrons. The photoelectrons are the number ejected from the surface of the photovoltaic cells when photons are incident on it.

So, the number of photoelectrons is equal to the number of photons incident on the metal surface per unit area, per unit time which is called the intensity of the incident light. So, in the photovoltaic cells, the photoelectric current produced is proportional to the intensity of incident light. Hence, statement A is false.

Using the kinetic energy relation of the ejected electron, when the wavelength of the incident light is increased the kinetic energy of the photoelectrons decreases and when it decreases then the kinetic energy increases. As the kinetic energy is proportional to the square of the speed, so the speed of the photoelectron also depends on the wavelength of the incident radiation.

Therefore, the correct option is D.

Note: The kinetic energy of the emitted electron is dependent on the frequency of the incident radiation. If the frequency is greater than the emitted electrons have maximum kinetic energy. The number of photoelectrons emitted is dependent on the intensity of the incident radiation.