Final answer:
Light is emitted when an electron transitions from a higher energy level to a lower one, releasing a photon in the process. This is observed in phenomena like the Balmer series transitions in hydrogen atoms.
Step-by-step explanation:
Light is emitted when an electron makes a transition to a lower energy level. The process of emission involves an electron dropping from a higher energy level to a lower one, releasing energy in the form of a photon. This phenomenon is observed in various scenarios, such as the fluorescence effect where an electron excited to a higher level returns to a lower level and emits light. For instance, in an electronic emission transition, light is emitted during the transition from a higher orbit to a lower orbit in the electron's path around the nucleus of an atom.
An example within the hydrogen atom is the Balmer series transitions, where an electron transitions from an orbit with n ≥ 3 to the orbit with n = 2. The energy difference between these levels corresponds to the visible portion of the electromagnetic spectrum, and light is emitted as the electron changes energy states.