What is the term for the bending of waves as they pass from one medium to another due to a change in their speed?

The term that describes the bending of waves as they pass from one medium to another due to a change in their speed is refraction. Refraction occurs when waves travel through materials with different densities, which impacts their speed and direction. When waves, such as light or sound, enter a new medium at an angle, they change speed; this change in speed results in a change in direction, causing the wave to bend. A common example of refraction is a straw appearing bent when it is placed in a glass of water; the light waves change speed as they transition between air and water, leading to the visual distortion.

In contrast, diffraction refers to the spreading of waves as they move around obstacles or through openings, and reflection is the bouncing back of waves when they hit a surface. Reflexion is simply an alternate term for reflection, largely considered outdated in contemporary usage. Understanding these concepts is essential in fields such as optics and acoustics, where wave behavior is a fundamental aspect of study.