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More slowly
- However, when light travels through a medium, it travels more slowly. The denser the medium the slower it gets. Water is denser than air, and so the path of light is hindered by more molecules than air and so it slows down more.
www.ck12.org/flexi/physical-science/refraction/why-is-light-slower-in-water-than-in-air/Why is light slower in water than in air? - CK-12 Foundation
Light will have the fastest velocity when it travels through the air. Light will have the slowest velocity when it travels through gelatin. Why? Light slows down when passing through different transparent materials. The more it slows down, the more it bends when it hits a medium made of that material.
Yes. Light travels slower through diamond than it does through glass, slower in glass than it does through water, slower through water than it does through air, and slower in air than it does through a vacuum.
Recall that light can travel through a medium, like air or water or glass. You can measure the speed of light in any of these media. You can also pass light through a vacuum where there is just empty space. Think of the light coming from the sun.
The speed of light in vacuum, commonly denoted c, is a universal physical constant that is exactly equal to 299,792,458 metres per second (approximately 300,000 kilometres per second; 186,000 miles per second; 671 million miles per hour).
- Theory of Light to the 19th Century: During the Scientific Revolution, scientists began moving away from Aristotelian scientific theories that had been seen as accepted canon for centuries.
- Double-Slit Experiment: By the early 19th century, scientists began to break with corpuscular theory. This was due in part to the fact that corpuscular theory failed to adequately explain the diffraction, interference and polarization of light, but was also because of various experiments that seemed to confirm the still-competing view that light behaved as a wave.
- Electromagnetism and Special Relativity: Prior to the 19th and 20th centuries, the speed of light had already been determined. The first recorded measurements were performed by Danish astronomer Ole Rømer, who demonstrated in 1676 using light measurements from Jupiter’s moon Io to show that light travels at a finite speed (rather than instantaneously).
- Einstein and the Photon: In 1905, Einstein also helped to resolve a great deal of confusion surrounding the behavior of electromagnetic radiation when he proposed that electrons are emitted from atoms when they absorb energy from light.
He also discovered that light travels faster in air than in water (confirming Arago's hypothesis), a fact that fellow countryman Foucault later confirmed through experimentation. Foucault employed a rapidly rotating mirror driven by a compressed air turbine to measure the speed of light.
Sound only travels at about 330 m/s through the air, so light is nearly a million times faster than sound. If lightning flashes 1 kilometre away from you, the light reaches you in 3 millionths of a second, which is almost instantly.
