The speed of light in a medium is typically slower than its speed in a vacuum. The speed of light in a medium is determined by its refractive index, which is a measure of how much the medium slows down the propagation of light compared to a vacuum.
To calculate the speed of light in a medium, you can use the formula:
v = c / n
where: v is the speed of light in the medium, c is the speed of light in a vacuum (approximately 299,792,458 meters per second), n is the refractive index of the medium.
Simply divide the speed of light in a vacuum by the refractive index of the medium to obtain the speed of light in that particular medium.