α-particle paths near a nucleus: impact parameter b and scattering angle θनाभिक के पास α-कणों के पथ: संघट्ट प्राचल b और प्रकीर्णन कोण θα-particle paths near a nucleus: impact parameter b and scattering angle θ

NCERT Fig 12.4 · Class 12 Physics · Chapter 12 · interactive diagram

Parts and what they mean

• Gold nucleus (charge +79e) (स्वर्ण नाभिक (आवेश +79e)) — About 50 times heavier than an α-particle, so it stays practically at rest. It repels the α-particle by Coulomb’s law: F = (1/4πε₀)(2e)(Ze)/r².
• Impact parameter b (संघट्ट प्राचल b) — Perpendicular distance of the initial velocity line of the α-particle from the centre of the nucleus.
• Scattering angle θ (प्रकीर्णन कोण θ) — Angle between the incoming direction and the final (outgoing) direction. Smaller b → larger θ.
• Paths with small impact parameter (छोटे संघट्ट प्राचल वाले पथ) — Particles aimed close to the nucleus feel a strong repulsion and turn through a large angle. These paths are hyperbolas, computed here from Coulomb’s law.
• Paths with large impact parameter (बड़े संघट्ट प्राचल वाले पथ) — Far from the nucleus the force is weak: the particle goes almost undeviated (θ ≈ 0). Most α-particles are like this.
• Head-on collision (b = 0) (आमने-सामने टक्कर (b = 0)) — The α-particle slows down, stops momentarily at the distance of closest approach and comes straight back (θ ≈ π).

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 12.4. Report a mistake