Question

How does the impact parameter affect the trajectory of an α-particle scattered by a heavy nucleus? What is the value of the impact parameter for a head-on collision of α-particles with the nucleus?

Answer 1

The impact parameter is the perpendicular distance between the initial direction of the α-particle and the center of the nucleus, and it controls the amount of deflection during scattering.

A larger impact parameter means the α-particle passes farther from the nucleus and undergoes only a small deflection, whereas a smaller impact parameter means it comes closer to the nucleus and is deflected more strongly.

For a head-on collision with the nucleus, the α-particle moves directly toward the center, so the impact parameter is zero.