That would depend what it enters from. If the light is transitioning from air to water,
its speed decreases. If it's going from jello to water, its speed increases.
Light waves change speed when they travel from air into the material of the pencil, and then change speed again when they exit the pencil back into the air. This change in speed causes the light waves to refract or bend.
The speed of light slows down ... in general, the denser the material, the lower the speed of light. (For example : air to water to glass.) The maximum speed is in a vacuum.
It seems to me that, to understand that, you need an understanding of the Huygens-Fresnel principle. Check the corresponding Wikipedia article; it has a nice illustration that shows how refraction is derived from this principle.
The speed of light is constant and does not change based on the material it passes through. However, when light enters a medium such as glass or water, its speed decreases due to interactions with the atoms in the material.
When light waves enter a material like glass or water, they slow down due to interactions with the atoms in the material. This change in speed is related to the optical density of the material, causing the light waves to bend, i.e., refract. Once the light waves exit the material, they resume their original speed in the air.
Slows IF it enters the water from air (and not - say - glass).
Because it slows down when entering water.
Yes, light bends when it enters a glass of water due to the change in speed as it moves from air into water, causing it to refract. This bending of light is known as refraction.
Light bends when it enters water due to a change in its speed caused by transitioning from one medium (air) to another medium with a different optical density (water). This change in speed causes the light waves to refract, or bend, at the boundary between the two mediums.
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.
Light will bend towards the normal as it enters water from air, due to the change in speed of light when it moves from one medium to another with a different optical density.
Light waves change speed when they travel from air into the material of the pencil, and then change speed again when they exit the pencil back into the air. This change in speed causes the light waves to refract or bend.
Laser light bends when passing through water due to a change in the speed of light as it enters a medium with a different refractive index. This change in speed causes the light to change direction, a phenomenon known as refraction.
No, light slows down when it moves from air to water due to the increase in the optical density of water compared to air. This change in speed causes the light to refract as it enters the water.
The speed of light slows down ... in general, the denser the material, the lower the speed of light. (For example : air to water to glass.) The maximum speed is in a vacuum.
When light enters a new medium, its speed can change. The speed of light changes depending on the optical density of the medium it is traveling through. In general, light travels more slowly in denser media such as glass or water compared to its speed in a vacuum.
The speed of light though substances is slower than the speed of light in a vacuum. As the light passes from air to water it slows and the ray's path is translated towards the normal to the air/water interface slightly.