Question

An electron with $KE$ $6eV$ is incident on a hydrogen atom in its ground state. The collision

• A. must be elastic.
• B. may be partially elastic.
• C. must be completely inelastic.
• D. may be partially inelastic.

Answer 1

The correct option is A must be elastic.

Minimum energy required for exciting a H atom from ground state
$(n=1)\to (n=2)$
$E=-13.6(\frac{1}{2^2}-1)$
$E_{min}=10.2eV$
So the H atom cannot absorb energy if the Energy is less than $10.2eV$, hence elastic collision.