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Question: Answered & Verified by Expert
A proton and an α-particle, having kinetic energies Kp and Kα, respectively, enter into a magnetic field at right angles. The ratio of the radii of the trajectory of proton to that of α -particle is 2:1. The ratio of Kp:Kα is:
PhysicsMagnetic Effects of CurrentJEE MainJEE Main 2021 (18 Mar Shift 2)
Options:
  • A 1:8
  • B 8:1
  • C 1:4
  • D 4:1
Solution:
1096 Upvotes Verified Answer
The correct answer is: 4:1

r=mvqB=pqB  mαmp=4

rprα=ppqpqαpα=21

pppa=2qpqa=212

pppα=1

KpKα=pp2pαpmαmp=14

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