Why do most elastic scattering curves show more neutrons scattering from an atomic nucleus at a small scattering angle than at a large one? Write a simple expression for the average scattering angle θ...

Why do most elastic scattering curves show more neutrons scattering from an atomic nucleus at a small scattering angle than at a large one?

Write a simple expression for the average scattering angle θ of a neutron scattering off of an atomic nucleus of weight A.