Question

Observe the following figure describing photoelectric effect in $Na$ & $Al$. Which, of the following statements, is correct ?

• A. $Na$ & $Al$ both have same threshold frequency
• B. Maximum kinetic energy, for both the metals, varies linearly on the frequency.
• C. The stopping potential will be same for both the metals, for the same frequency
• D. $Al$ is more photo sensitive than $Na$.

Answer 1

The correct option is B Maximum kinetic energy, for both the metals, varies linearly on the frequency.

$K{E}_{max}=E-{\varphi }_0$

On comparing with y=mx+c
we can conclude that it is a linear variation.
So, $K{E}_{max}$ varies linearly with frequency, for both the metals.

From the graph, it is clear that both the metals have different threshold frequency.
Also, $(f_0{)}_{Na}<(f_0{)}_{Al}$. So, $Na$ is more photo sensitive than $Al$.
As both metals have different work functions, they will have different stopping potentials, for the same frequency.

Hence, $\left(B\right)$ is the correct answer.

$$\begin{array}{c}\text{Why this Question ?}\\ \text{This question tests the dependency \& variation of max possible KE; with respect to frequency of incident radiation.}\end{array}$$