Explain the impact parameter ?

Impact Parameter :
→ The impact parameter of the α -particle is defined as the perpendicular distance of the velocity vector of the α -particle from the centre of the nucleus, when the α -particle is far away from the nucleus of atom.
→ It is denoted by b.
$\therefore \mathrm{b}=\frac{{\mathrm{ze}}^2\cot (\mathrm{\theta }/2)}{4\mathrm{\pi }{\in }_0\left(\frac{1}{2}{\mathrm{mv}}^2\right)}$
→ Where ' $\mathrm{\theta }$ ' is scattering angle.
→ If value of 'b' is large, then scattering angle ' $\mathrm{\theta }$ ' will be small. Therefore, the $\mathrm{\alpha }$ -particles suffer small deflection.
→ If the value of 'b' is small, then scattering angle ' $\mathrm{\theta }$ ' will be large. Therefore, the $\mathrm{\alpha }$ -particles suffer large deflection.
→ If b = 0 then $\mathrm{\theta }$ =180°, therefore $\mathrm{\alpha }$ -particle is directed towards the centre of the nucleus.