Light will slow down if it goes through just about anything that is not a vacuum, for example air, glass, water.
No, light does not speed up in water, it slows down.
If your speed slows down, yYou will have negative acceleration or deceleration.
In a vacuum, light travels at its maximum speed. When passing through a non-opaque substance, such as glass or water, the speed of light slows down due to interactions with the atoms in the material. Among common substances, light generally slows down the most in materials with a high refractive index, such as diamond.
When a car slows down at a traffic light, it is decelerating. This means that the car is reducing its speed or coming to a stop in response to the signal.
No. Light slows down whenever it passes through water. Nothing is faster than the speed of light in a vaccum.
Slows IF it enters the water from air (and not - say - glass).
No, slower. Light travels fastest in a vacuum. Anything transparent that light can pass through slows it down somewhat. Diamond crystal slows it down notably, which is part of what causes the "fire" in a diamond.
If you mean "normal speed" to be the speed at which light travels in a vacuum, then no. Anything that differs from light moving through a vacuum slows the light down to a certain extent.
No, the speed of light is not the same in every medium. It slows down when it passes through materials like water or glass.
Light slows down in water because it interacts with the molecules in the water, causing it to change direction and speed. This interaction results in a decrease in the speed of light as it travels through the water.
This is part of the Special Theory of Relativity.
The speed of light decreases when it enters a denser medium and is refracted, such as water or glass. The change in speed causes the light to change direction at the boundary between the two media.