\(r=\frac{m v}{q B}=\frac{\sqrt{2 m e V}}{e B}=\frac{1}{B} \sqrt{\frac{2 m}{e} V}\)
\(\Rightarrow \quad V=\frac{B^{2} r^{2} e}{2 m}=0.8 \mathrm{V}\)
For transition between \(3\) to \(2\) .
\(E=13.6\left(\frac{1}{4}-\frac{1}{9}\right)=\frac{13.6 \times 5}{36}=1.88 \,eV\)
Work function \(=1.88 \mathrm{eV}-0.8 \mathrm{eV} \)
\(=1.08 \mathrm{eV} \approx 1.1 \mathrm{eV}\)