In any substance, all electromagnetic waves travel at the same speed
that light travels through that substance.
Chat with our AI personalities
In a vacuum the speed of red and blue light are the same as all light, 300,000,000m/s. Their frequency and wavelength will be different but the speed remains the same.
* E = total energy, * m = mass, * c = the speed of light in a vacuum
There are several different types of glass, and light has a somewhat different speed in each of them. On the average, the speed of light across all typical types of glass is in the neighborhood of 2/3 its speed in vacuum, or around 200,000 km/sec .
This is called the index of refraction. When light crosses the boundary between mediums (media) with different indices, it is bent (refracted).It's usually defined the other way around ... the ratio of the speed of light in vacuum to its speed in the medium. Since the speed of light is greater in vacuum than in any medium, the number is always greater than 1. It's referred to as the "refractive index" of the medium.
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.