- #1
lolgarithms
- 120
- 0
I have heard that the speed of light remains c even if it is not in a vacuum. the light bounces around in the substance a bit, so light appears to have slowed down. Is this true?
This is true on a microscopic level, but not what we tell high school or college freshmen physics students.DrGreg said:When photons of light pass through a material, each photon still travels at c, but when it hits an atom, it gets absorbed. Then there's a short delay before another photon is emitted, at c, continuing in the same direction. So the light gets delayed through the medium and the average speed is less than c.
DrGreg said:That's the over-simplified version, easy to understand, but actually not true in quantum-mechanical terms. For the full story, see the https://www.physicsforums.com/showpost.php?p=899393&postcount=4
raphael3d said:i wonder how far one can slow down c in various solid state materials and i little thought experiment: what if n -> infinity ? would that imply that the transparent material is so dense, that light would take an infinit long time to pass?
raphael3d said:yes missed it.
many thanks for the link, very interesting indeed.
but it hasnt anything to do with slowing down photons at all, rather using tricks which seem to have the same effect, like quantum beaming, which isn't really beaming, more transforming states. same here.
the bose-einstein-condensate is a bit closer to what i want, but the process is described above...again kind of a trick. it seems to me that photons aways travel with 3x10^8 m/s but with different times of arrival in different mediums. by deforming space too, light follows a longer path, but with the same velocity it takes longer to arrive at some point. the bottom line is in every example longer times in traveling but with constant velocity c
please correct me if i have written ******** =)
kind regards
The speed of light in a medium refers to the speed at which light travels through a substance other than a vacuum. This speed is typically slower than the speed of light in a vacuum, which is approximately 299,792,458 meters per second.
Light slows down in a medium because it interacts with the particles of the substance, causing it to be absorbed and re-emitted. This process takes time and thus, slows down the overall speed of light in the medium.
The speed of light in a medium can affect our perception in various ways, depending on the substance. For example, the speed of light in water is about 75% of the speed of light in a vacuum, which is why objects appear distorted when viewed through water.
No, the speed of light in a medium is not constant and can vary depending on the properties of the medium, such as its density, temperature, and composition. For example, light travels slower in denser mediums such as glass or diamond compared to less dense mediums like air.
The speed of light in a medium can be measured using various techniques, such as measuring the time it takes for light to travel a known distance in the medium or using the refractive index of the medium. The refractive index is a measure of how much the speed of light is reduced in a medium compared to a vacuum.