The speed of light is greatest in vacuum, and somewhat less in any material medium.
The exact number depends on the individual material. They're all different.
About 2/3 its speed in a vacuum.
The speed of light is minimum in Glass. It is because light travels at minimum speed in solids.
glass
Speed of light in vacuum = ' c '-- Speed of light in Air . . 99.97% of ' c '.-- in Water . . . . . . . . 75% of ' c '.-- in Crown Glass . . . 64.9%-- in Flint Glass . . . . . 61.7%-- in Diamond . . . . . . 41.3%
Light travels at a slower speed in glass compared to vacuum. The ratio of the speed of light in vacuum to the speed of light in glass is called the refractive index of glass. So, the distance light travels in glass would be the distance it travels in vacuum divided by the refractive index of glass.
it travels at c (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 .
3/4th
It will depend on the type of glass, and something called its refractive index. All materials have a refractive index which will effect the speed of the light through it. The speed of light through a vacuum is 3.0x10^8 m/s, and a material such as glass will be lower than this.
The refractive index of flint glass is 1.6, approx. This means that the speed of light in flint glass is 1/1.6 of its speed in vacuum. This makes it 187,380,000 metres per second.
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.
In glass, light will go somewhat slower than in a vacuum. Air is almost like a vacuum, with respect to the speed of light - some difference still exists, though.In glass, light will go somewhat slower than in a vacuum. Air is almost like a vacuum, with respect to the speed of light - some difference still exists, though.In glass, light will go somewhat slower than in a vacuum. Air is almost like a vacuum, with respect to the speed of light - some difference still exists, though.In glass, light will go somewhat slower than in a vacuum. Air is almost like a vacuum, with respect to the speed of light - some difference still exists, though.