In a vacuum, photons travel faster than in liquid water.
Photons move at the speed of light, or roughly 299,792,458 meters per second (186,282 miles per second), in a vacuum, like space.
However, because of interactions between the photons and the medium’s atoms or molecules, light moves a little more slowly in a material medium, such as liquid water, than it does in a vacuum. Light travels at about 225,000,000 meters per second in water, which is roughly 3/4 of its speed in a vacuum.
The medium’s refractive index, which measures how much light is slowed down when it travels through a substance as opposed to a vacuum, is the cause of this speed differential.
In a vacuum, photons travel faster than in liquid water.
Photons move at the speed of light, or roughly 299,792,458 meters per second (186,282 miles per second), in a vacuum, like space.
However, because of interactions between the photons and the medium’s atoms or molecules, light moves a little more slowly in a material medium, such as liquid water, than it does in a vacuum. Light travels at about 225,000,000 meters per second in water, which is roughly 3/4 of its speed in a vacuum.
The medium’s refractive index, which measures how much light is slowed down when it travels through a substance as opposed to a vacuum, is the cause of this speed differential.