Abeam of o - particles of energy 4 kev with a rate of 3x108 particles/s strikes a target, a 10- μm thick aluminum foil. a detector of cross-sectional area 400 mm2 is placed 0.6 m from the target in a direction at 60° to the beam direction. considering the scattering of a-particle on an al nucleus as the scattering on a fixed center, find the rate of detection of o-particles. (atomic mass of al-27 u, where 1 u = 1.66×10-27 kg; atomic number of al-13; density ofal p 1 ev = 1.6. 10-19., the constant kin the coulomb's law is k = 9.109 n m2/c) = 2.71p kg/m3; atomic number of α-particle is 2; e = 1 .6. 10-19 c;