The bending of a wave as it moves from one medium to another is called refraction. This occurs due to a change in the wave's speed as it enters the new medium. Here's a breakdown:

* Why does the speed change? The speed of a wave depends on the properties of the medium it's traveling through. For example:

* Light: Travels faster in air than in water or glass.

* Sound: Travels faster in solids than in liquids or gases.

* How does the speed change affect direction? The change in speed causes the wave to bend, or refract. Here's the key principle:

* If the wave slows down: It bends towards the normal (an imaginary line perpendicular to the surface between the two media).

* If the wave speeds up: It bends away from the normal.

Here's an analogy: Imagine you're walking on a beach and you suddenly encounter a patch of soft sand. Your speed decreases. To keep walking in the same direction, you'll need to adjust your path slightly towards the harder sand. The wave does something similar as it transitions between mediums!

The amount of bending depends on:

* The difference in speed between the two media: The greater the difference, the more the wave bends.

* The angle at which the wave strikes the surface: A wave hitting the surface at a steep angle will bend more than one hitting at a shallow angle.

Refraction is a common phenomenon that we see in our everyday lives:

* A straw appearing bent in a glass of water: Light slows down in water, causing it to bend towards the normal.

* A rainbow: Sunlight refracts through water droplets, separating the different colors of light.

* Magnifying glasses: Light bends as it passes through the lens, causing objects to appear larger.

Let me know if you'd like to explore any of these examples in more detail!