\(\frac{h c}{\lambda}=\frac{h c}{632.2 \times 10^{-9}}\)
\(\frac{h c}{\lambda}=e V+w_0\)
\(e V=\frac{h c}{\lambda}-w_0\)
\(V=\frac{h c}{e} \times \frac{1}{\lambda}-\frac{w_0}{e}\)
\(\tan \theta=\frac{h c}{e}=\) constant [Slope of \(V\) vs \(\frac{1}{\lambda}\) graph]
\(\therefore \theta\) is same for all metals.