JEE Mains · Physics · STD 12 - Dual nature of radiation and matter
- JEE Mains 2026
- Medium
- MCQ
The graph shows variation of stopping potential \(V_o\) with the frequency \(\nu\) of the incident radiation for three photosensitive metals \(X_1\), \(X_2\) and \(X_3\). Which metal will give out electrons with greater kinetic energy, for the same wavelength of incident radiation?

Pick an option to check your answer.
Answer & Solution
Correct Answer
(A) \(X_1\)
Step-by-step Solution
Detailed explanation
From Einstein's photoelectric equation, the maximum kinetic energy of emitted photoelectrons is given by:
\(K_{\text{max}} = \dfrac{hc}{\lambda} - \Phi\)
where \(\lambda\) is the wavelength of incident radiation and \(\Phi\) is the work function of the metal.
The work function is related to the threshold frequency \(\nu_0\) by \(\Phi = h\nu_0\). From the given graph, the x-intercept represents the threshold frequency. We can observe that:
\(\nu_0(X_1) < \nu_0(X_2) < \nu_0(X_3)\)
Therefore, the work functions of the metals follow the order:
\(\Phi(X_1) < \Phi(X_2) < \Phi(X_3)\)
For the same wavelength \(\lambda\) of incident radiation, the term \(\dfrac{hc}{\lambda}\) is constant. Thus, the kinetic energy \(K_{\text{max}}\) will be greatest for the metal with the smallest work function.
Since metal \(X_1\) has the minimum work function, it will emit electrons with the greatest kinetic energy.
Answer: \(X_1\)
\(K_{\text{max}} = \dfrac{hc}{\lambda} - \Phi\)
where \(\lambda\) is the wavelength of incident radiation and \(\Phi\) is the work function of the metal.
The work function is related to the threshold frequency \(\nu_0\) by \(\Phi = h\nu_0\). From the given graph, the x-intercept represents the threshold frequency. We can observe that:
\(\nu_0(X_1) < \nu_0(X_2) < \nu_0(X_3)\)
Therefore, the work functions of the metals follow the order:
\(\Phi(X_1) < \Phi(X_2) < \Phi(X_3)\)
For the same wavelength \(\lambda\) of incident radiation, the term \(\dfrac{hc}{\lambda}\) is constant. Thus, the kinetic energy \(K_{\text{max}}\) will be greatest for the metal with the smallest work function.
Since metal \(X_1\) has the minimum work function, it will emit electrons with the greatest kinetic energy.
Answer: \(X_1\)
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