Question

Answer the attachment.....

Given
¢ = work function = 4.0 eV


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Answer 1

if $\large\rm { λ_{0}}$ be the threshold wavelength and $\large\rm { λ}$ be the wavelength of incident light, the condition for photoelectron emission is $\large\rm { λ < λ_{0}}$

Thus, threshold wavelength is the longest wavelength for photoelectron emission.

So fork function : $\large\rm { W = \frac {hc}{λ_{0}}}$

$\large\rm { λ_{0} = \frac {hc}{W} = \frac {(6.62 × 10^{-34} )(3 × 10^{8}}{4×1.6×10^{-19}}}$

$\large\rm { = 310 \ nm}$