The figure shows the variation of photocurrent with anode potential for a photo-sensitive surface fo

Question

The figure shows the variation of photocurrent with anode potential for a photo-sensitive surface for three different radiations. Let $I_a, I_b$ and $I_c$ be the intensities and $f_a, f_b$ and $f_c$ be thc frequencies for the curves $a, b$ and $c$ respectively.

Professor PC Thomas Classes · Answer

1. Frequency $(f)$ and Stopping Potential $\left(V_0ight)$ :
Stopping potential is determined by the frequency of incident radiation. From the graph, curves $a$ and $b$ meet the x -axis at the same point:
$$
V_{0 a}=V_{0 b} \Longrightarrow f_a=f_b
$$2. Intensity ( $I$ ) and Saturation Current ( $i_{	ext {sat }}$ ):
Saturation current is determined by the intensity of incident radiation. From the graph, curves $a$ and $b$ have different maximum y -values:
$$
i_{s a t, a}<i_{s a t, b} \Longrightarrow I_a 
eq I_b
$$3. Conclusion:
Combining the observations gives $f_a=f_b$ and $I_a 
eq I_b$.