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A neutron moving with a speed ‘v’ makes a head on collision with a stationary hydrogen atom in ground state.  The minimum kinetic energy of the neutron for which inelastic collision will take place is :

  • Option 1)

    10.2 eV

  • Option 2)

    16.8 eV

  • Option 3)

    12.1 eV

  • Option 4)

    20.4 eV


Answers (1)


As we learnt in

Inelastic Collision -

Can happen when energy of neutron is grater than 20.4 ev ,

but not equal to 20.4 ev, 24.18 ev, 25.5 ev,26.18 ev (etc )

- wherein

Energy exchanged is less than K.E.of neutron


 If kinetic energy of neutron is K.

The amount of energy exchanged in perfectly inelastic collision =\frac{K}{2}

But \frac{K}{2}\geq10.2\ eV (energy difference between ground state and first excited state)

K\geq20.4\ eV

Correct option is 4

Option 1)

10.2 eV

This is an incorrect option.

Option 2)

16.8 eV

This is an incorrect option.

Option 3)

12.1 eV

This is an incorrect option.

Option 4)

20.4 eV

This is the correct option.

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