Physics - Modern Physics Question with Solution | TestHub

From the relation, $eV=\frac{hc}{\lambda }-\varphi$ or $V=\left(\frac{hc}{e}\right)\left(\frac{1}{\lambda }\right)-\frac{\varphi }{e}$ This is equation of straight line. Slope is $\tan \theta =\frac{hc}{e}$ $$\begin{array}{rl}{\varphi }_1:{\varphi }_2:{\varphi }_3& =\frac{hc}{{\lambda }_{01}}:\frac{hc}{{\lambda }_{02}}:\frac{hc}{{\lambda }_{03}}=\frac{1}{{\lambda }_{01}}:\frac{1}{{\lambda }_{02}}:\frac{1}{{\lambda }_{03}}=1:2:4\\ \frac{1}{{\lambda }_{01}}& =0.001{\mathrm{nm}}^{-1}\text{ or }{\lambda }_{01}=10000\mathring{A}\\ \frac{1}{{\lambda }_{02}}& =0.002{\mathrm{nm}}^{-1}\text{ or }{\lambda }_{02}=5000\mathring{A}\\ \frac{1}{{\lambda }_{03}}& =0.004{\mathrm{nm}}^{-1}\text{ or }{\lambda }_{03}=25000\mathring{A}\end{array}$$ Violet colour has wavelength $4000\mathring{A}$. So, violet colour can eject photoelectrons from metal-1 and metal-2.