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Question: Answered & Verified by Expert
An α - particle of energy 5 MeV is scattered through 180° by a fixed Uranium nucleus. The distance of the closest approach is (Atomic number of uranium = 92)
PhysicsNuclear PhysicsNEET
Options:
  • A 5.3×10-12 m
  • B 5.3×10-13 m
  • C 5.3×10-14 m
  • D 5.3×10-15 m
Solution:
2646 Upvotes Verified Answer
The correct answer is: 5.3×10-14 m
According to the law of conservation of energy,

The kinetic energy of α - particle = Potential energy of alpha α - particle at a distance of closest approach.

⇒  12mv2=14πε0q1q2r

⇒  5 MeV=9×1092e92er

r=5.3×10-14 m

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