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STD 12 - 12. atoms — NEET STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceNEETSTD 12 - 12. atoms4 Marks
MCQ
An electron collides with a free molecule initially in its ground state. The collision leaves the molecule in an excited state that is metastable and does not decay to the ground state by radiation. Let $K$ be the sum of the initial kinetic energies of the electron and the molecule and $p$ be the sum of their initial momenta. Let $K^{\prime}$ and $p ^{\prime}$ represent the same physical quantities after the collision. Then,
  • A
    $K=K^{\prime}, p = p ^{\prime}$
  • ✓
    $K^{\prime} < K, p = p ^{\prime}$
  • C
    $K=K^{\prime}, p \neq p ^{\prime}$
  • D
    $K^{\prime} < K, p \neq p ^{\prime}$
✓

Answer

Correct option: B.
$K^{\prime} < K, p = p ^{\prime}$
b
(b)

Part of kinetic energy of incoming electron is absorbed by molecule and it gets into excited state.

So, kinetic energy after collision is reduced (collision is inelastic).

Linear momentum is conserved as momentum conservation holds correct for elastic as well as inelastic collision.

So, $\quad K^{\prime} < K$ and $p ^{\prime}= p$

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