What does refractor mean?
A refractor is an object, substance, or optical instrument that causes light to change direction when it passes through a boundary between media of different refractive indexes. This bending, called refraction, depends on the materials involved: light passing from air into glass or water generally turns toward the normal to the boundary. In astronomy, a refractor is a telescope that uses an objective lens to gather and focus light, producing a sharp, inverted image. The term can therefore describe either the general physical cause of refraction or a specific optical instrument. Refractors are particularly associated with observing stars, planets, and other distant objects, while other instruments may be better suited to observing large areas of the sky. Understanding the word connects everyday experiences such as a bent drinking straw in water with the design and purpose of astronomical telescopes.
An object or substance that refracts a ray of light, changing its direction as it passes from one medium into another.
"The prism acted as a refractor and split the white light into its component colors."
This is a technical optical term and is less common in general speech.
A telescope that uses a lens or mirror to collect and focus light onto an eyepiece or detector.
"The historic refractor remains in use for visual observations of the night sky."
In astronomy, the word commonly serves as a shortened form of refracting telescope.
The plural is used when referring to multiple refracting objects or refracting telescopes.
"The observatory houses several small refractors for visual observation."
A refractor turns light’s journey into a detour—without moving the light itself, it can make a distant image appear close and clear.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does refractor come from?
The word was formed in the early 19th century from the Latin stem refract-, meaning “broken,” the same root used in refraction and reflective-related terminology. English had already borrowed refract from Latin, where it described light being broken in direction at a boundary between transparent substances. The suffix -or forms a noun denoting an instrument or object that performs an action.
Related word forms
How refractor is actually used
In optics, the term is chiefly technical and refers to an object that causes light to refract. In astronomy, it is commonly used for a refracting telescope and may be distinguished informally from a reflecting telescope.