Problem 6.12

A narrow beam of alpha particles with kinetic energy $T$ $=0.50 \mathrm{MeV}$ falls normally on a golden foil whose mass thickness is $\rho d=1.5 \mathrm{mg} / \mathrm{cm}^{2} .$ The beam intensity is $I_{0}=5.0 \cdot 10^{5}$ particles per second. Find the number of alpha particles scattered by the foil during a time interval $\tau=30 \mathrm{~min}$ into the angular interval: (a) $59-61^{\circ}$ (b) over $\theta_{0}=60^{\circ}$