Final answer:
The emission of light in electronic transitions occurs when an electron moves from a higher energy level to a lower one, often releasing a photon. This process is exemplified by the Balmer series in hydrogen atoms.
Therefore, the correct option is: D) Electron transition from a higher to a lower energy level.
Step-by-step explanation:
The electronic transition that involves the emission of light occurs when an electron transitions from an excited state to a lower energy state.
During this process, the energy difference between the higher and lower energy states is released in the form of electromagnetic radiation, or light.
A classic example of such transitions is observed in the Balmer series of hydrogen, where electrons fall from higher energy levels (n ≥ 3) to the second energy level (n = 2), emitting light that is visible to the human eye.
This phenomenon is governed by the law of conservation of energy, which asserts that the energy emitted (as a photon) when an electron returns to a lower energy state is equivalent to the energy that was initially absorbed to excite the electron to the higher energy level.
Thus, only option D, 'electron transition from a higher to a lower energy level', accurately describes the electronic transition that involves the emission of light.