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the theory that light is transmitted as waves

In optics, the theory which regards light as a mode of motion generated by molecular vibrations in the luminous source, and propagated by undulations in a subtle medium (ether), sensibly imponderable, presumed to pervade all space, including the intervals which separate the molecules or atoms of ponderable bodies. When these undulations reach and act on the nerves of our retina, they produce in us the sensation of light. The only other theory of light which can be opposed to this, and which is variously called the corpuscular, emission, or material theory, supposes light to consist of material particles, emitted from the source, and projected in straight lines in all directions with a velocity which continues uniform at all distancses, and is the same for all intensities. It would seem that every phenomenon which can be brought under the corpuscular theory can with equal facility be explained by the undulatory theory; while there are some known effects, as the phonomena of reflection and refraction, in strict accordance with the principles of the latter, which cannot, without great difficulty and the introduction of gratuitous suppositions, be accounted for by the corpuscular theory. The undulatory theory is therefore now generally adopted by physicists.

Doctrine that light, electricity, and heat are propagated by undulations in an ether which pervades all space.