Q69 / 90 · KVPY 2016 (SB/SX) · Physics

An electron with kinetic energy $E$ collides with a hydrogen atom in the ground state. The collision will be elastic

  • A
    For all values of $E$
  • Correct answer
    B
    For $10.2 \mathrm{eV} < \mathrm{E} < 13.6 \mathrm{eV}$ only
  • C
    For $\mathrm{E} < 10.2 \mathrm{eV}$
  • D
    For $0 < \mathrm{E} < 3.4 \mathrm{eV}$ only

Solution

When $\mathrm{e}^{-}$collide with atom which is massive in comparison to $\mathrm{e}^{-} .$Max possible loss of $\mathrm{KE}=\mathrm{KE}$ of $\mathrm{e}^{-}($initial $\mathrm{KE})=\mathrm{E}$ if this $\mathrm{E}$ is less than min excitation energy then collision is elastic $\therefore \mathrm{E} < 10.2 \mathrm{eV}$ (Minimum excitation energy)

Hence, the correct answer is option: 'B'.

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