Neutrons (mass 1) are being scattered by a nucleus of mass A(A > 1). In the center of the mass system the scattering is isotropic. Then, in the lab system the average of the cosine of the angle of deflection of the neutron is A cos 0 +1 Jo (A² +2ACOS e + 1)/² 1 (cos v) = sine do. Show, by expansion of the denominator, that (cos v) = 2/3A.

Neutrons (mass 1) are being scattered by a nucleus of mass A(A > 1). In the center of the mass system the scattering is isotropic. Then, in the lab system the average of the cosine of the angle of deflection of the neutron is A cos 0 +1 Jo (A² +2ACOS e + 1)/² 1 (cos v) = sine do. Show, by expansion of the denominator, that (cos v) = 2/3A.