Question

An electron of energy $11.2eV$ undergoes an inelastic collision with a hydrogen atom in its ground state. [Neglect recoiling of atom as $m_H>>m_e$]. Then in this case

• A. The outgoing electron has energy $11.2eV$
• B. The entire energy is absorbed by the $H$ atom and the electron stops
• C. $10.2eV$ of the incident electron energy is absorbed by the $H$ atom and the electron would come out with $1.0eV$ energy
• D. None of the above

Answer 1

Answer: (C)

$10.2eV$ of the incident electron energy is absorbed by the $H$ atom and the electron would come out with $1.0eV$ energy

Now, the collision between electron and H-atom is inelastic which means that the Kinetic Energy before and after collision is not same.

Since $m_H>>m_e$ thus the majority of energy of the electron will be absorbed by the H-atom and the electron will travel with remaining energy.

Thus, $10.2eV$ of the incident electron energy is absorbed by the H-atom and the electron would come net with $1.0eV\Rightarrow \left(c\right)$ energy.