Question

A photon of $10.2eV$ energy collides with a hydrogen atom in ground state inelastically. After few microseconds, one more photon of energy $15eV$ collides with the same hydrogen atom. Then what can be detected by a suitable detector?

• A. One photon of $10.2eV$ and an electron of energy $1.4eV$
• B. $2$ Photon of energy $10.2eV$
• C. $2$ Photon of energy $3.4eV$
• D. $1$ Photon of $3.4eV$ and one electron of $1.4eV$

Answer 1

The correct option is A One photon of $10.2eV$ and an electron of energy $1.4eV$

A photon of $10.2eV$ energy collides with a hydrogen atom in ground state inelastically this will not cause any transition but only scatter with its full energy so we can detect a photon of $10.2eV$. After few microseconds one more photon of energy $15eV$ collides with the same hydrogen atom which cause an ionization of an electron from its ground state. So we can detect another electron with energy $(15-13.6)=1.4eV$.