A Level Physics Practice Exam

When an electron transitions to a lower energy level, what does it emit?

1. Gravitons

2. Photons

3. Neutrinos

4. Electrons

The correct answer is: Photons

When an electron transitions to a lower energy level, it emits photons. This emission occurs because, in quantum mechanics, electrons exist in discrete energy levels around an atom's nucleus. When an electron moves from a higher energy state to a lower one, it loses energy. To conserve energy, the electron releases this energy difference in the form of a photon, which is a quantum of electromagnetic radiation. Photons have varying energies, which correspond to the difference between the two energy levels involved in the transition. Therefore, each transition emits a photon with a specific wavelength and energy, which can often be observed as spectral lines in the emission spectrum of the atom. This process is fundamental in various applications, including lasers and spectroscopy, where electron transitions are responsible for the light emitted by these systems. The other choices do not relate to electron transitions in atoms; gravitons are theoretical particles associated with gravity, neutrinos are nearly massless particles produced in nuclear reactions, and electrons themselves would not be emitted in this context as they pertain to the same type of particle involved in energy level transitions.