Question

In Rutherford scattering experiment, what will be the correct angle for $\alpha -$scattering, for an impact parameter $b=0$?

• A. ${90}^0$
• B. ${270}^0$
• C. $0^0$
• D. ${180}^0$

Answer 1

The correct option is D ${180}^0$

Impact parameter is given as:-
$b=\frac{1}{4\pi {ϵ}_0}\frac{Z{e}^2\cot \frac{\theta }{2}}{E}$

Here, $b\propto cot\frac{\theta }{2}$

When $b=0$, $\cot \frac{\theta }{2}=0$

$\Rightarrow \theta ={180}^0$

Therefore, an alpha particle travelling directly towards the centre of a nucleus, will retrace its path.

Hence, $\left(D\right)$ is the correct answer.

$$\begin{array}{c}\text{Why this Question?}\\ \text{This question is based on impact parameter and it will make the concept of impact parameter more clear.}\end{array}$$