Assertion (A) The impact parameter for α -particles by 180^ is zero. Reason (R) Zero impact parameter means that the α -particles tend to hit the centre of the nucleus.

Correct answer: A. Both A and R are true and R is a correct explanation for A . Impact parameter, b=(z e^2 (θ)/(2))/(4 π _0((1)/(2) m v^2)) For θ=180^ , 90^ =0 , impact parameter, b=0 Hence, α -particles tend to hit the centre of nucleus. Thus, both A and R are true and R is a correct explanation for A .

NEET

Exam: NEET
Subject: Physics
Chapter: Atomic Physics

NEET · Physics · Atomic Physics

Assertion (A) The impact parameter for α -particles by 180^ is...

Assertion (A) The impact parameter for

\alpha

-particles by

180^{\circ}

is zero. Reason (R) Zero impact parameter means that the

\alpha

-particles tend to hit the centre of the nucleus.

Options

ABoth $\mathrm{A}$ and $\mathrm{R}$ are true and $\mathrm{R}$ is a correct explanation for $A$ .
BBoth $\mathrm{A}$ and $\mathrm{R}$ are true but $\mathrm{R}$ is not a correct explanation for $\mathrm{A}$ .
C $\mathrm{A}$ is true but $\mathrm{R}$ is false.
D $\mathrm{A}$ is false but $\mathrm{R}$ is true.

Correct answer

A. Both $\mathrm{A}$ and $\mathrm{R}$ are true and $\mathrm{R}$ is a correct explanation for $A$ .

Step-by-step solution

Impact parameter,

b=\frac{z e^2 \cot \frac{\theta}{2}}{4 \pi \varepsilon_0\left(\frac{1}{2} m v^2\right)}

For

\theta=180^{\circ}, \cot 90^{\circ}=0

, impact parameter,

b=0

Hence,

\alpha

-particles tend to hit the centre of nucleus. Thus, both

\mathrm{A}

and

\mathrm{R}

are true and

\mathrm{R}

is a correct explanation for

\mathrm{A}

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