A beam of electrons of energy E scatters from a target having atomic spacing of 1. The first maximum intensity occurs at θ=60^°. Then E (in eV) is \…

A beam of electrons of energy E scatters from a target having atomic spacing of $\displaystyle 1 \AA$. The first maximum intensity occurs at $\displaystyle \theta=60^{\circ}$. Then E (in eV) is \_\_\_\_. (Planck constant $\displaystyle \mathrm{h}=6.64 \times 10^{-34} \mathrm{Js}$, $$1 \mathrm{eV}=1.6 \times 10^{-19} \mathrm{~J}, $$ electron mass $\displaystyle m=9.1 \times 10^{-31} \mathrm{~kg}$ )