What is an array of entities ordered by a common physical property like wavelength called?

An array of entities ordered by a common physical property such as wavelength is known as a spectrum. In astronomy and physics, a spectrum typically refers to the distribution of electromagnetic radiation based on its wavelength or frequency. When light or other forms of electromagnetic radiation pass through a prism or diffraction grating, it is separated into its constituent colors or wavelengths, creating a spectrum.

This concept is foundational in many areas of astronomy, as spectroscopic analysis allows scientists to determine the composition, temperature, density, and motion of celestial objects. For instance, astronomers can infer the chemical elements present in a star by studying the absorption or emission lines within its spectrum.

The other terms provided do not accurately capture the essence of ordered arrays based on physical properties. A matrix refers to a rectangular array of numbers, symbols, or expressions arranged in rows and columns, commonly used in mathematics. A field typically refers to a physical or mathematical concept that describes a particular region or distribution of quantities (like a gravitational or electric field). A chart, while it can represent data visually, does not imply an ordering based on a common physical property like wavelength. Thus, the term spectrum is the most appropriate and precise to describe this ordering uniformity.