Question

A photon collides with a stationary hydrogen atom in the ground state inelastically. Energy of the colliding photon is $10.2eV$. Almost instantaneously, another photon collides with the same hydrogen atom inelastically with an energy of $15eV$. What will be observed by the detector?

• A. Two photons of energy $10.2eV$
• B. Two photons of energy $1.4eV$
• C. One photon of energy $10.2eV$ and one electron of energy $1.4eV$
• D. One electron having kinetic energy nearly $11.6eV$

Answer 1

The correct option is D One electron having kinetic energy nearly $11.6eV$

Enregy of nth orbit in hydrogen atom is given by:
$E_n=-\frac{13.6}{n^2}eV$
Thus, energy of first and second orbit is $-13.6eV,-3.4eV$ respectively.
Therefore, on collision of photon with energy $10.2eV$, electron will move from 1st orbit to 2nd orbit.
Then, photon of energy $15eV$ results in ionization and leaves $11.6eV$ energy to the electron.
The energy thus obtained is converted to Kinetic energy.