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kolleamm
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According to my physics book light changes speed in different mediums such as water. Doesn't the speed of light have to remain constant?
Thanks in advance
Thanks in advance
No.kolleamm said:Is light changing speed a relatively new discovery?
That is a widely held, but incorrect, belief. There is a recent thread on this. I suggest a forum search.rcgldr said:I had the impression that In the case of light going through a medium, the apparent speed slows down due to the rate that electrons absorb and emit photons, but that the speed of the photons as they travel unimpeded remains the same.
rcgldr said:I had the impression that In the case of light going through a medium, the apparent speed slows down due to the rate that electrons absorb and emit photons, but that the speed of the photons as they travel unimpeded remains the same.
Thanks. At least I know why I had that impression (might have been related to propagation inside of a laser). I wondered what percentage of light is actually captured and re-emitted while traveling through a medium such as glass.phinds said:That is a widely held, but incorrect, belief. There is a recent thread on this. I suggest a forum search.
See post #2kolleamm said:So light can change speed? It doesn't always travel at 186,000 mi/s ?
https://www.physicsforums.com/insights/do-photons-move-slower-in-a-solid-medium/phinds said:That is a widely held, but incorrect, belief. There is a recent thread on this. I suggest a forum search.
The speed of light is a physical constant that is defined as approximately 299,792,458 meters per second in a vacuum.
According to the theory of relativity, the speed of light is a fundamental constant and cannot be changed. However, there are some theories that suggest the speed of light may have been different in the early universe.
The speed of light is affected by the medium it is traveling through. It travels slower in materials such as water or glass compared to a vacuum. It is also affected by gravity; light bends when passing through a strong gravitational field.
There have been experiments that have claimed to measure a slight variation in the speed of light, but these have not been widely accepted by the scientific community. The current consensus is that the speed of light is constant and cannot be changed.
The speed of light plays a crucial role in many fundamental laws and equations in physics, such as the famous E=mc² equation. It also serves as a constant in the theory of relativity, which has greatly shaped our understanding of the universe.