Answer:
a quantum release of energy as electrons drop back to their ground state
Step-by-step explanation:
Niels Bohr discovered the phenomena of light he saw that as the electrons go around the energy levels towards the centre, they give up a photon of light. .
In this way, a quantum release of energy as electrons drop back to their ground state complies to "the law of conservation of energy"
Phenomena is caused by absorption or emission of energy, as exemplified in a Hydrogen atom that can be hit , giving up protons and observed as a specific line in the spectrum
We know today thanks to that that visible light is formed by all colours of the spectrum
When we use a prism, the light splits into the spectrum:
There is a Visible spectrum and invisible spectrum
When an electron falls back it gives ups a colour, according to the level of energy it falls back from.
In the image below you can see how an atom's electrons like hydrogen can look like