Refraction
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Refraction is the change in direction of a wave, caused by the change in the wave's speed. Examples of waves include sound waves and light waves. Refraction is seen most often when a wave passes from a medium to a different medium. Different types of medium include air and water. When a wave passes from one medium to another medium, the wave will change its velocity and its direction. For example, when a light wave travels through air and then passes through water, the wave's speed will slow down and it will change direction.
An example of how refraction works is placing a straw in a cup of water, with part of the straw in the water. When looking at a certain angle, the straw appears to bend at the water's surface. This is because of the bending of light rays as they move between the air and the water.
