A Level Physics Practice Exam

What happens when electrons move down an energy level?

1. A photon is absorbed

2. A photon is emitted

3. An electron is added

4. An energy level is created

The correct answer is: A photon is emitted

When electrons move down an energy level, they transition from a higher energy state to a lower energy state. This release of energy occurs in the form of a photon, which is a particle of light. The energy of the emitted photon corresponds to the difference in energy between the two levels. In the context of atomic structure, when an electron occupies a higher energy level, it can become excited, requiring energy to maintain that state. When it drops to a lower energy level, the excess energy must be released, and this is accomplished by emitting a photon. This principle is fundamental to understanding phenomena such as atomic emission spectra, where the emitted photons correspond to specific wavelengths of light. The other options do not accurately describe what occurs during this transition. For instance, absorption of a photon would happen when an electron moves up an energy level, while adding an electron or creating an energy level does not pertain to the existing electron's transition between energy states. Thus, emitting a photon is the correct outcome when electrons move down an energy level.