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The light of two different frequencies whose photons have energies 3.8 eV and 1.4 eV respectively, illuminate a metallic surface whose work function is 0.6 eV successively. The ratio of maximum speeds of emitted electrons for the two frequencies respectivly will be :

Option: 1

1:1


Option: 2

2:1


Option: 3

4:1


Option: 4

1:4


Answers (1)

best_answer

 Work function =\mathrm{\phi_{0}=0.6 \mathrm{eV}}
\begin{array}{l} h f_{1}=3.8 \mathrm{eV} \\ h f_{2}=1.4 \mathrm{eV} \end{array}

From Einstein equation of photoelectric effect,
\begin{array}{l} h f=\phi_{0}+\frac{1}{2} m v_{\max }^{2} \\ \\ \therefore h f_{1}-\phi_{0}=\frac{1}{2} m v_{1}^{2} \rightarrow(1) \\ \\ h f_{2}-\phi_{0}=\frac{1}{2} m v_{2}^{2} \rightarrow(2) \\ \\ (1) \div(2) \\ \\ \frac{3 \cdot 2}{0 \cdot 8}=\frac{v_{1}^{2}}{v_{2}^{2}} \\ \\ \frac{v_{1}}{v_{2}}=2 \end{array}
The correct option is (2)

Posted by

rishi.raj

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