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 <10.2eV
• C. for E <13.6eV
• D. for E < 3.4eV

Answer 1

The correct option is B for E <10.2eV

Electron will not excite the hydrogen atom & all its KE will involve in elastic collision.
$E_2-E_1>KE$
$E_{e}V<-3.4-(-13.6)$
$E<10.2eV$