What phenomenon occurs when various frequencies of light are absorbed by an atom?

Fluorescence occurs when various frequencies of light are absorbed by an atom. In this process, an atom absorbs a photon of light, which excites an electron to a higher energy level. Once the electron is in this higher energy state, it eventually returns to its ground state, releasing energy in the form of a photon. This emitted light is often of a longer wavelength than the absorbed light, resulting in a phenomenon where the emitted light can appear as a different color.

This process is distinct from other options. For example, photon multiplication does not directly refer to the absorption process but rather deals with a nonlinear interaction of light and matter. Energy resonance relates to the specific frequencies at which atoms can absorb energy, but it does not specifically describe the resultant emission of light. Photon emission describes the release of energy when an atom de-excites, but does not encompass the initial absorption of light across various frequencies. Fluorescence uniquely highlights both the absorption and subsequent re-emission of light, making it the correct choice in this context.