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  • Sodium and copper have work functions and <img alt="4.5 \mathrm{~eV}" src="https://en

Sodium and copper have work functions 2.3 \mathrm{~eV} and 4.5 \mathrm{~eV}respectively. Then, the ratio of their threshold wavelengths is nearest to:

Option: 1

1:2


Option: 2

2:1


Option: 3

1:4


Option: 4

4:1


Answers (1)

best_answer

\begin{aligned} &\text{Work function, } \mathrm{W}_0=h \mathrm{v}_0\\ &\text{For sodium, } \mathrm{W}_{01}=\mathrm{hv}_{01}=\frac{\mathrm{hc}}{\lambda_0}\\ & =\frac{2.3 \mathrm{eV}}{\mathrm{h}}=\mathrm{v}_{01}=\frac{\mathrm{c}}{\lambda_{01}} \\ & \text { For copper, } \mathrm{W}_{02}=\mathrm{hv}_{02} \\ & =\frac{4.5 \mathrm{eV}}{\mathrm{h}}=\mathrm{v}_{02}=\frac{\mathrm{c}}{\lambda_{02}} \\ & =\frac{\lambda_{01}}{\lambda_{02}}=\frac{\mathrm{ch}}{2.3} \times \frac{4.5}{\mathrm{ch}}=\frac{2}{1} \\ & \Rightarrow \lambda_{01}: \lambda_{02}=2: 1 \end{aligned}

Posted by

Pankaj Sanodiya

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