The work function of a metal is 3 eV. The color of the visible light that is required to cause emission of…

The work function of a metal is 3 eV. The color of the visible light that is required to cause emission of photoelectrons is
  1. Green
  2. Blue
  3. Red
  4. Yellow

Solution

$\begin{aligned}
& (\mathrm{KE})_{\max }=\frac{\mathrm{hc}}{\lambda}-\phi \\ & \frac{\mathrm{hc}}{\lambda} \gt \phi[\text { for emission }] \\ & \lambda \lt \frac{\mathrm{hc}}{\phi} \Rightarrow \lambda \lt \frac{1242}{3} \mathrm{~nm}
\end{aligned}$
So blue light option (B)

Asked in: JEE Main 2025 (03 Apr Shift 1)

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