Einstein’s theory of relativity is founded on the **speed of light being constant**. However, there are postings and scientific discussions where there is mention of “**light slowing down traveling through materials”**. Does it really slow down in the material or is the entrance/exit delay explained by something else?
For example, would it instead be explained that the photons are absorbed and then re-generated on the other side of atoms as they make their way through water, glass, etc? The “delay” is then actually a measure of the time spent between absorption and emission?
In: 6
The light does actually go slower through a medium.
The wave version of this is that the EM field of the light interacts with the charged elements of the atoms in the vicinity that it is traveling through. These charges are disturbed and generate their own EM waves with the same frequency at which they were excited (the light’s frequency), but with a different phase. These waves when summed with the incident light wave (superposition) result in a wave that is going slower than the light in a vacuum.
The light does actually go slower through a medium.
The wave version of this is that the EM field of the light interacts with the charged elements of the atoms in the vicinity that it is traveling through. These charges are disturbed and generate their own EM waves with the same frequency at which they were excited (the light’s frequency), but with a different phase. These waves when summed with the incident light wave (superposition) result in a wave that is going slower than the light in a vacuum.
Yes, the propagation velocity changes based on the dielectric constant of the material. For fiberglass (FR4 to be specific) circuit boards, which make up 99% of what goes in electronics, the propagation velocity is roughly half the normal speed of light.
Certain ceramic materials can have even higher dielectric constants (in the tens and hundreds), which allow antennas to be much smaller.
Yes, the propagation velocity changes based on the dielectric constant of the material. For fiberglass (FR4 to be specific) circuit boards, which make up 99% of what goes in electronics, the propagation velocity is roughly half the normal speed of light.
Certain ceramic materials can have even higher dielectric constants (in the tens and hundreds), which allow antennas to be much smaller.
Yes, the propagation velocity changes based on the dielectric constant of the material. For fiberglass (FR4 to be specific) circuit boards, which make up 99% of what goes in electronics, the propagation velocity is roughly half the normal speed of light.
Certain ceramic materials can have even higher dielectric constants (in the tens and hundreds), which allow antennas to be much smaller.
Light slows down in a medium. Basically, the electric fields of the atoms slow down the light’s propagation.
What special and general relativity rely on is the speed of causality to be the same for all observers. The speed of causality is the fastest possible speed that any two things can interact at. Light moves at this speed in a vacuum because there are no electric fields to slow it down, and it has no mass, so it moves at the fastest possible speed, the speed of causality.
Gravitational waves also move at the speed of causality because they, too, have no mass and therefore nothing to slow them down.
We often use the speed of light and speed or causality interchangeably, but that’s because in most situations, they are the same speed.
Light slows down in a medium. Basically, the electric fields of the atoms slow down the light’s propagation.
What special and general relativity rely on is the speed of causality to be the same for all observers. The speed of causality is the fastest possible speed that any two things can interact at. Light moves at this speed in a vacuum because there are no electric fields to slow it down, and it has no mass, so it moves at the fastest possible speed, the speed of causality.
Gravitational waves also move at the speed of causality because they, too, have no mass and therefore nothing to slow them down.
We often use the speed of light and speed or causality interchangeably, but that’s because in most situations, they are the same speed.
Light slows down in a medium. Basically, the electric fields of the atoms slow down the light’s propagation.
What special and general relativity rely on is the speed of causality to be the same for all observers. The speed of causality is the fastest possible speed that any two things can interact at. Light moves at this speed in a vacuum because there are no electric fields to slow it down, and it has no mass, so it moves at the fastest possible speed, the speed of causality.
Gravitational waves also move at the speed of causality because they, too, have no mass and therefore nothing to slow them down.
We often use the speed of light and speed or causality interchangeably, but that’s because in most situations, they are the same speed.
The “speed of light” means two different things.
One meaning is it’s the fundamental speed limit imposed on us by the very geometry of space-time. Massless particles travel at this speed in a vacuum, so that’s also the speed of photons (ie, light), in a vacuum.
Another meaning is “here’s some light, how fast is it traveling?” and the fact is, that depends on what it’s traveling through. Whether they’re being absorbed and re-transmitted, or actually traveling slowly, might just end up being an argument over the best words to describe the maths.
The “speed of light” means two different things.
One meaning is it’s the fundamental speed limit imposed on us by the very geometry of space-time. Massless particles travel at this speed in a vacuum, so that’s also the speed of photons (ie, light), in a vacuum.
Another meaning is “here’s some light, how fast is it traveling?” and the fact is, that depends on what it’s traveling through. Whether they’re being absorbed and re-transmitted, or actually traveling slowly, might just end up being an argument over the best words to describe the maths.
Latest Answers