A neutron beam of energy E scatters from atoms on a surface with a spacing $d= 0.1 nm$ . The first maximum of initially in the reflected beam occurs at $ \theta= 30^{\circ}$ . What is the kinetic energy E of the beam in eV?

Question

$\begin{array}{1 1} 0.082\;kev \\ 0.082\;mev \\ 0.082\;ev \\ 0.082\;Gev \end{array} $