A 25nm photon is going into a gas of hydrogen atoms all in the ground state. Whi

Question

A 25nm photon is going into a gas of hydrogen atoms all in the ground state. Which is a possible result?

A) Only 13.6 eV is absorbed. The electron is liberated from the atom and the photon continues with the excess energy.

B)The atom absorbs the photon, and the electron leaves with the excess Kinetic energy

C) It is impossible for the atom to absorb the photon

D) One hydrogen atom would absorb 13.6eV of energy and others would absorb the rest of the photon energy.

We know from previous knowledge, Hydrogen in ground state has the energy of 13.6eV

Looking for the correct answer, but more importantly, why the other options are incorrect

Explanation / Answer

Important point to note: A Photon can be visualized as a single packet of energy, which can only be absorbed completely by a single atom. It's energy can neither be absorbed partially, nor by a number of atoms.

A) From the point above, it is clear that partial energy can't be absorbed from the photon. So, A is false.

C) It is possible for the atom to absorb the photon. Difference between ground state(-13.6 eV) and first excited state of hydrogen(-3.4 eV) is 10.2 eV. So, any photon with energy greater than or equal to 10.2 eV is absorbed and the electron goes to higher energy levels, or completely out of the atom.

So, C is false.

D) Again from the point mentioned above, partial absorption is not possible. So, D is false.

B) The photon is absorbed by the atom. 13.6eV energy of the photon is used to escape from the nucleus. The remaining energy will be converted to Kinetic Energy of the electron.

So, B is TRUE.

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