Here's why:

* Electronic Transitions: These involve the movement of electrons from one energy level to another within an atom or molecule.

* Energy Levels: Electrons can only occupy specific energy levels, and they need to absorb energy to jump to a higher level.

* UV and Visible Light: The energy carried by photons of UV and visible light matches the energy differences between electronic energy levels in many atoms and molecules.

How it works:

1. When a photon of UV or visible light strikes an atom or molecule, the energy of the photon is absorbed by an electron.

2. This absorbed energy excites the electron, causing it to transition from a lower energy level to a higher one.

3. The electron then quickly returns to its ground state, releasing the absorbed energy as a photon of light.

Note: Infrared (IR) radiation causes vibrational transitions, and microwaves cause rotational transitions.