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Electrons with maximum kinetic energy  3 \mathrm{eV} are ejected from a metal surface by ultraviolet radiation of wavelength: 1500 \mathrm{~A}^{\circ} what is the threshold wavelength of metal.

 

Option: 1

2350 \mathrm{~A}^{\circ}


Option: 2

2460 A^{\circ}


Option: 3

2500 A^{\circ}


Option: 4

2560 \mathrm{~A}^{\circ}


Answers (1)

best_answer

The energy of incident photon in eV is
E=\frac{12420}{1500} \mathrm{eV}=8.28 \mathrm{eV}
According to photoelectric effect equation, we have


\begin{aligned} & E=\phi+K \cdot E_{\text {max }} \Rightarrow \phi=E-K \cdot E_{\text {max }} \\ & \phi=8.29 \mathrm{ev}-3 \mathrm{eV}=5.29 \mathrm{eV} . \end{aligned}

\Rightarrow The threshold wavelength for the metal surface corresponding to the work function 5.29 \mathrm{eV}  is given as


\lambda_{\text {th }}=\frac{12420}{5.29} \mathrm{~A}^{\circ}=2350 \mathrm{~A}^{\circ}

Posted by

SANGALDEEP SINGH

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