Q. A neutron collides head on with a stationary hydrogen atom in ground state. Which of the following statements are correct (Assume that the hydrogen atom and neutron has same mass)

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A

If kinetic energy of the neutron is less than 20.4 e V collision must be elastic

B

If kinetic energy of the neutron is less than 20.4 eV collision may be inelastic

C

Inelastic collision may be take place only when initial kinetic energy of neutron is greater than 20.4 eV

D

Perfectly inelastic collision can not take place

Solution:

For inelastic collisions the maximum possible energy loss in a collision should be more than the minimum energy required for excitation of any of the colliding atoms which in this case is $10.2\, eV$ for hydrogen atom. As the hydrogen atom and neutron are of same mass, maximum kinetic energy loss can be the half of initial kinetic energy of the colliding particle hence in above case initial kinetic energy must be more than or equal to $20.4\, eV$ for inelastic collision

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