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