# Wave refraction

One characteristic of waves is refraction. Refraction occurs when a wave that originally traveled through one medium enters a different medium. For example, a sound wave initially moves through the air and then encounters a wall, some sound waves are reflected by the wall, some are refracted by the wall. Refraction means that sound waves are absorbed or transmitted in the wall, but the direction of propagation changes. The change in the direction of propagation occurs because the speed of the sound wave changes when it enters a different medium from the previous medium. The angle between the incident ray and the normal is called the angle of incidence, while the angle between the refracted ray and the normal is called the angle of refraction.

If the speed of the wave increases when it enters a new medium, the angle of refraction also increases. Conversely, if the speed of the wave decreases when it enters a new medium, then the angle of refraction also decreases.

For example, a sound wave moves from air into water, so the speed of the sound wave decreases. Or earthquake waves travel from the ground to the rocks, reducing the speed of the waves. Conversely, the speed of the wave increases when moving from a denser medium to a less dense medium.

Have you ever played at the beach? If you pay close attention, the direction of the sea waves in the middle of the ocean doesn’t always go to the beach.

But as it gets closer to the beach, the direction of the sea waves is getting parallel to the beach. This happens because of the refraction of sea waves. The Law of Refraction During the same time interval, wavefront 1 moves a distance of l1 = v1 t and wavefront 2 moves a distance of l2 = v2 t. Where v1 is the speed of the wave in medium 1, such as air, and v2, is the speed of the wave in medium 2, such as water. P is the same, so both formulas simplify to: 