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A low intensity uv light of wavelength  2271 \mathrm{~A}^{\circ} irradiates a photocell made of molybdenum metal. If the stopping potential is 1.3 \mathrm{~V},  what is the work function of the metal.

Option: 1

4.0 \mathrm{ev}


Option: 2

3.87 \mathrm{ev}


Option: 3

4.17 \mathrm{ev}


Option: 4

4.52 \mathrm{ev}


Answers (1)

best_answer

Energy of incident photon is
E=\frac{12420}{2271} \mathrm{ev}=5.47 \mathrm{eV} \text {. }


As stopping potential for ejected electron is 1.3 \mathrm{~V}, the maximum k .E. of ejected electron will be


k \cdot E_{\max }=e V_0=1.3 \mathrm{eV} \text {. }
from photoelectric effect equation


\begin{aligned} \phi & =E-K \cdot E_{\max } \\ & =(5.47-1.3) \mathrm{eV}=4.17 \mathrm{eV} . \end{aligned}

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Gaurav

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