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The speed of light (and all other forms of electromagnetic radiation) in vacuum is determined by
the electrostatic permittivity (ε0) and magnetic permeability (μ0) of free space.

An interesting thought ... we have no way of knowing whether these physical constants are the same
numbers today that they have always been. If either of them has changed since the birth of the universe,
then the speed of light changed, and our observations of the earliest cosmos give an erroneous number
for the age of the universe.

But anyway, that's what these quantities are today, and they're what determines the speed of light,
as is so neatly predicted by Maxwell's equations and verified spot-on by the best measurements.

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15y ago
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5mo ago

The speed of light in a vacuum is determined by fundamental physical constants, specifically the permittivity and permeability of free space. It is a universal constant, denoted as "c," with a value of approximately 299,792,458 meters per second.

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Related questions

How can the nature of the source of light wave can influence the speed of light in a vacuum?

The speed of light in a vacuum is constant at about 3 x 10^8 meters per second. The nature of the source of the light wave does not directly influence the speed of light in a vacuum. The speed of light is determined by physical constants in the vacuum, such as the permeability and permittivity of free space.


Why speed of light is constant in vaccum?

Because the speed of light is determined by the electrical characteristics of the medium, and the electrical characteristics of vacuum don't change.


Is speed related to the color of a light wave?

No, speed of light is constant in a vacuum at approximately 299,792 kilometers per second. The color of a light wave is determined by its frequency and wavelength, not its speed.


Why is the speed of light limited in a vacuum?

The speed of light is not limited in a vacuum - the speed of light is fastest in a vacuum. But that is what Einstein called the "Cosmic Speed Limit" - nothing can move faster than the speed of light in a vacuum, or even quite asfast.


What is the speed of light through the liquid whose refractive index you have determined?

If the refractive index is k then the speed of light is c/k metres per second where c is the speed of light in vacuum (approx 299,792,458 m/s).


Does laser light color affect the speed at which it travels?

No, the color of laser light does not affect its speed. All light travels at the same speed in a vacuum, which is approximately 299,792 kilometers per second. The color of light is determined by its wavelength and frequency.


Does the speed of light change in a vacuum?

No, not as long as the light stays in vacuum.No, it does not. That is where it has its maximum speed.


What happens to frequency does the speed of light ever change?

The speed of light IN A VACUUM is always the same. In substances other than the vacuum, the speed of light is usually slower than in a vacuum.


How is the speed of an electromagnetic wave determined?

The speed of an electromagnetic wave is determined by the properties of the medium it is traveling through. In a vacuum, electromagnetic waves travel at the speed of light, which is approximately 299,792 kilometers per second. This speed can change when the wave enters a different medium.


What is the speed of light of a vacuum?

In vacuum, the speed is 299,792,458 meters per second.


How does the average speed of light glass compare with its speed in a vacuum?

About 2/3 its speed in a vacuum.


What percentage of the speed of light in vacuum is the speed of light in water?

The speed of light in water is about 75% of the speed of light in a vacuum. This is due to the higher refractive index of water, which slows down the speed of light as it passes through the medium.