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Emission theory or extramission theory (variants: extromission) or extromissionism is the proposal that visual perception is accomplished by eye beams emitted by the eyes. This theory has been replaced by intromission theory (or intromissionism ), which is that visual perception comes from something representative of the object (later ...
There were two major ancient Greek schools, providing a primitive explanation of how vision works. The first was the "emission theory" of vision which maintained that vision occurs when rays emanate from the eyes and are intercepted by visual objects. If an object was seen directly it was by 'means of rays' coming out of the eyes and again ...
Before the Book of Optics was written, two theories of vision existed. The extramission or emission theory was forwarded by the mathematicians Euclid [6] and Ptolemy, [7] who asserted that certain forms of radiation are emitted from the eyes onto the object which is being seen.
Emission theory may refer to: Emission theory (relativity), a former competing theory for the special theory of relativity; Emission theory (vision), ...
Ibn al-Haytham was the first to correctly explain the theory of vision, [14] and to argue that vision occurs in the brain, pointing to observations that it is subjective and affected by personal experience. [15] He also stated the principle of least time for refraction which would later become Fermat's principle. [16]
The name most often associated with emission theory is Isaac Newton.In his corpuscular theory Newton visualized light "corpuscles" being thrown off from hot bodies at a nominal speed of c with respect to the emitting object, and obeying the usual laws of Newtonian mechanics, and we then expect light to be moving towards us with a speed that is offset by the speed of the distant emitter (c ± v).
He used similar arguments to show that the ancient emission theory of vision supported by Ptolemy and Euclid (in which the eyes emit the rays of light used for seeing), and the ancient intromission theory supported by Aristotle (where objects emit physical particles to the eyes), were both wrong. [2]
In the physics inherited from Plato [1] (although rejected by Aristotle [2]), an eye beam generated in the eye was thought to be responsible for the sense of sight.The eye beam darted by the imagined basilisk, for instance, was the agent of its lethal power, given the technical term extramission.