The radiation corresponding to $\;3 \to 2\;$ transition of hydrogen atom falls on a metal surface to produce photoelectrons . These electrons are made to enter a magnetic field of $\;3 \times 10^{-4}\;T\;$. If the radius of the largest circular path followed by these electron is 10.0 mm ,the work function of the metal is close to :

Question

$(a)\;1.8\;eV \qquad(b)\;1.1\;eV\qquad(c)\;0.8\;eV\qquad(d)\;1.6\;eV$