RE-NEET 2026 Physics Rutherford Scattering MCQ Question

✅ Answer: B

📚 NCERT Topic: Structure of Atom Subtopic: Rutherford’s α-particle Scattering Experiment

🔍 Explanation

The number of α-particles scattered at angle $\theta$ follows Rutherford’s relation:

$$\boxed{N(\theta)\propto \frac{1}{\sin^4(\theta/2)}}$$

As $\theta$ increases, $\sin(\theta/2)$ increases, so:

$$\boxed{\theta\uparrow \Rightarrow N(\theta)\downarrow\text{ rapidly}}$$

At small angles, many α-particles are scattered; at large angles, the number becomes very small.

Therefore, the graph should show a very steep decrease initially, followed by a long low tail → B.

❌ Why other options are wrong

• A ❌ Decrease is too gradual; it does not represent the strong $\csc^4(\theta/2)$ dependence.
• C ❌ Shows a maximum at intermediate angle; Rutherford scattering does not behave this way.
• D ❌ Shows increasing $N(\theta)$, opposite to the relation.

📖 NCERT Line

“Most of the fast moving α-particles passed straight through the gold foil, with only a small fraction being deflected through large angles.”

⚡ QUICK REVISION

$$\boxed{N(\theta)\propto\csc^4(\theta/2)}$$

Small $\theta$ → many particles Large $\theta$ → very few particles $180^\circ$ → extremely few/back-scattered

🧠 Graph trick: Steep fall → long tail = Rutherford scattering → B.