As light rays pass from one medium into another, they bend (or "refract"). This can be easily seen by trying to poke at something under water from above the surface (for example, aim a drinking straw at a target in a glass of water). This refraction is a consequence of the change in direction due to the wave-qualities of light, as the speed of the light is affected by the change of medium.
When light waves pass from one medium to another, they may be refracted, reflected, or both. Refraction occurs when the speed of light changes as it enters a new medium, causing the light to bend. Reflection occurs when the light waves bounce off the surface of the new medium.
It must pass though a medium from an another medium.
refraction
If light waves change speed as they pass from one medium into another at an angle, the light will be refracted, meaning it will bend as it enters the new medium. This bending is due to the change in speed of the light wave.
The bending of light rays when they travel from one medium to another is known as refraction. This occurs because light waves change speed and direction as they pass from a medium with one optical density to a medium with a different optical density. The amount of bending is determined by the refractive indices of the two media.
This is called refraction. It occurs when light waves change speed as they move from one medium to another, causing them to bend.
diffraction
Refraction is the bending of light waves as they pass from one medium to another.
Refraction is the bending of light waves when they pass through another substance. This phenomenon occurs due to a change in the speed of light as it travels from one medium to another, causing the light waves to change direction.
The bending of light rays when they pass from one medium to another is called refraction. This phenomenon occurs due to the change in the speed of light as it moves from a medium with one refractive index to a medium with a different refractive index.
you ask me
If your talking about wavelengths, like in light, it might change depending on the medium it moves trough...