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 magentic field of $3 \times 10^{-4}T$ . If the radius of the largest circular path followed by these electrons is $10.0\; mm$, the work function of the metal is close to :

Question

$\begin{array}{1 1}(A)\;0.8\;eV \\ (B)\;1.6\;eV \\(C)\;1.8\;eV \\(D)\;1.1\;eV \end{array}$