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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?

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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: \(X_1\)
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