Question

An electron with kinetic energy =E eV collides with a hydrogen atom in the ground state. The collision will be elastic
A. for all values of E
B. for `E lt 10.2 eV`
C. for `E lt 13.6 eV`
D. only for `E lt 3.4 eV`

Answer 1

Correct Answer - C
A collision will be inelastic if some part of incident K.E. utilised in exciting the atom. The minimum energy required to excite the hydrogen atom (n=1 to n=2) is 10.2 eV
If `E lt 10.2`eV, no question of excitation of atom.