Answer
The atom undergoes a stimulated emission transition. The incident photon causes the atom in the $ p $ state to transition to the $ s $ state, emitting another photon with the same energy (2.0 eV).
Work Step by Step
The photon with energy 2.0 eV is incident on an atom that is initially in the $ p $ state (energy = 2.0 eV).
The available energy levels for the atom are:
- $ s $ state: 0.0 eV
- $ p $ state: 2.0 eV
- Another $ s $ state: 3.0 eV
So the possible transitions are:
1. Absorption Transition: For an absorption transition to occur, the atom would need to absorb the photon's energy and move to a higher energy level. The energy difference between the $ p $ state (2.0 eV) and the higher $ s $ state (3.0 eV) is 1.0 eV.
Since the incident photon has an energy of 2.0 eV, it does not match the required energy (1.0 eV) for the atom to absorb the photon and transition to the higher $ s $ state.
Therefore, absorption is not possible.
2. Stimulated Emission Transition: For stimulated emission to occur, the atom must be in an excited state and a photon with energy matching the difference between the excited state and a lower energy state must be incident, causing the atom to emit a photon of the same energy. The difference between the $ p $ state (2.0 eV) and the lower $ s $ state (0.0 eV) is exactly 2.0 eV, which matches the energy of the incident photon.
Therefore, the incident photon can stimulate the atom to undergo a transition from the $ p $ state to the $ s $ state, resulting in the emission of an additional photon with the same energy (2.0 eV).
