In a vacuum, where there are no intervening particles or medium, the speed of light is constant and is approximately 299,792,458 meters per second (denoted as 'c'). This speed is a fundamental constant in physics and is the maximum speed at which information or energy can travel in the universe according to our current understanding.
In different materials or mediums, such as air, water, or glass, the speed of light can be slower than its speed in a vacuum. This is due to the interaction of light with the particles or atoms in the medium, which can cause the light to be absorbed and re-emitted multiple times, resulting in a slower overall propagation speed.
The speed of light in a specific medium is denoted as 'v,' and it is generally less than 'c.' The ratio of the speed of light in a vacuum to the speed of light in a medium is called the refractive index (n) of that medium. The refractive index determines how much the light is slowed down in that particular medium.
So, to answer your question, light cannot go faster than its speed in a vacuum (c) in any medium. It can only travel at speeds slower than c, depending on the refractive index and the properties of the medium it is passing through.