Question

Explain giving reasons for the following.
(a) Photoelectric current in a photocell increases with the increase in the intensity of the incident radiation.
(b) The stopping potential $\left(V_0\right)$ varies linearly with the frequency $\left(\nu \right)$ of the incident radiation for a given photosensitive surface with the slope remaining the same for different surfaces.
(c) Maximum kinetic energy of the photo-electrons is independent of the intensity of incident radiation.

Answer 1

A)Photoelectric current in a photocell increases with increases in frequency,

$\frac{1}{\lambda }=\frac{\varphi }{hc}$

As per equation,

The intensity of light increases, the saturation current increases, This is because a larger number of photons now fall on the metal surface and hence a larger number of electrons interact with photons. The number of electrons emitted increases and hence the current increases.

B) We know,

$tan\theta =\frac{hc}{e}$

The slope of the photocurrent is same for every surface.

C)The maximum kinetic energy of a stream of the photoelectron is determined by the measuring the stopping potential (the applied voltage needed keep the photoelectrons trapped in the photoemissive surface).Increases linearly with the frequency of the incident light above the threshold frequency is independent of the intensity of the incident light.