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  4. The work function for aluminium surface is 4.2 eV. The cut-off wavelength for the photoelectric effect is

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Q. The work function for aluminium surface is 4.2 eV. The cut-off wavelength for the photoelectric effect is

Dual Nature of Radiation and Matter

Solution:

If $ \lambda_0 $ is threshold wavelength, then work function
$ \phi_0 = \frac{ h c }{ \lambda_0 } $
$ \Rightarrow \lambda_0 = \frac{ h c }{ \phi_0 } $
= $ \frac{ 6.6 \times 10^{ - 34 } \times 3 \times 10^8 }{ 4.2 \times 1.6 \times 10^{ - 19 }} $
$\approx 2955$ $\mathring{A}$