A steady beam of alpha particles (q = +2e) traveling with constant kinetic energy 20 MeV carries a current of 0.25 $\displaystyle \mu A$.

(a) If the beam is directed perpendicular to a flat surface, how many alpha particles strike the surface in 3.0s?

(b) At any instant, how many alpha particles are there in a given 20 cm length of the beam?

(c) Through what potential difference is it necessary to accelerate each alpha particle from rest to bring it to an energy of 20 MeV?