Distance of Closest Approach r o = 1 / 4π ε o . 2Ze 2 / E k where , E k = kinetic energy of the cc-particle .
Impact Parameter
The perpendicular distance of the velocity vector of a-particle from the central line of the nucleus , when the particle is far away from the nucleus is called impact parameter .
Impact parameter
where , Z = atomic number of the nucleus , E k = kinetic energy of the c-particle and θ = angle of scattering .
Rutherford ’ s Scattering Formula
where , N ( θ ) = number of c-particles , N i = total number of α-particles reach the screen . n = number of atoms per unit volume in the foil , Z = atoms number , E = kinetic energy of the alpha particles and t = foil thickness