In Rutherford's scattering experiment, if impact parameter b = 0, then the value of the scattering angle will be:

180°

The correct answer is Option (3) → 180°

In Rutherford's scattering experiment, the impact parameter (b) is defined as the perpendicular distance from the center of the nucleus to the initial velocity vector of the incoming particle.

If impact parameter $b=0$, the scattering angle is 180°.