Q78 / 90 · JEE Main 2024 (06 Apr Shift 2) · Physics

When UV light of wavelength $300 \mathrm{~nm}$ is incident on the metal surface having work function $2.13 \mathrm{eV}$, electron emission takes place. The stopping potential is: (Given hc $=1240 \mathrm{eV} \mathrm{nm}$ )

  • A
    $1.5 \mathrm{~V}$
  • B
    $4.1 \mathrm{~V}$
  • Correct answer
    C
    $2 \mathrm{~V}$
  • D
    $4 \mathrm{~V}$

Solution

$\begin{aligned} & \frac{\mathrm{hc}}{\lambda}-\phi=\mathrm{e} . \mathrm{V}_{\mathrm{s}} \\ & \Rightarrow \frac{1240}{300} \mathrm{eV}-2.13 \mathrm{eV}=\mathrm{eVs} \\ & \Rightarrow 4.13 \mathrm{eV}-2.13 \mathrm{eV}=\mathrm{eVs} . \\ & \Rightarrow \text { So, } \quad \mathrm{V}_{\mathrm{s}}=2 \mathrm{volt}\end{aligned}$

Hence, the correct answer is option: 'C'.

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