Physics - Modern Physics Question with Solution | TestHub

The work function of material is given by $$\begin{array}{rl}& \varphi =\mathrm{hv}\\ & \varphi =\frac{\mathrm{hc}}{\lambda }\end{array}$$ $$\text{ ..(i) }\left[\because v=\frac{c}{\lambda }\right]$$ where, $\mathrm{h}=$ Planck's constant $=6.63\times 10^{-34}\mathrm{J}-\mathrm{s}$ $\mathrm{c}=$ speed of length $=3\times 10^8{\mathrm{ms}}^{-1}$ and $\lambda =$ wavelength of light Here, $\varphi =4\mathrm{eV}=4\times 1.6\times 10^{-19}\mathrm{J}$ Substituting the given values in Eq. (i), we get $\Rightarrow 4\times 1.6\times 10^{-19}=\frac{6.63\times 10^{-34}\times 3\times 10^8}{\lambda }$ or $\lambda =\frac{6.63\times 10^{-34}\times 3\times 10^8}{4\times 1.6\times 10^{-19}}$ $=3.108\times 10^{-7}\mathrm{m}\simeq 310\mathrm{nm}$