Here's why:

* Refraction is the bending of a wave as it passes from one medium to another. This bending occurs because the wave's speed changes as it enters the new medium.

* Why the speed changes: The speed of a wave is determined by the properties of the medium it travels through. Different mediums have different densities and other characteristics that affect how easily the wave can propagate. For example, light travels faster in air than in water.

Here's a simple analogy:

Imagine you're walking on a sidewalk and then suddenly step onto a grassy area. Your speed will likely change as you transition from the hard sidewalk to the softer grass. This change in speed is similar to what happens to a wave when it refracts.

Examples of refraction:

* Light: When light passes from air to water, it bends because it slows down in water. This is why a straw in a glass of water appears to be broken at the water's surface.

* Sound: Sound waves also refract, which is why sound can travel further at night. The temperature difference between the ground and the air can cause sound waves to bend upwards during the day, but downwards at night.

Let me know if you'd like more details about refraction or have any other questions.