Final answer:
Refraction occurs when a wave enters a new medium, leading to a change in direction and speed. This happens due to different properties, such as density or depth, which affect the waves' speed and wavelength.
Step-by-step explanation:
When a wave is refracted, it changes direction and speed as it enters a new medium or material. This bending of the path is due to the change in wave speed and is often accompanied by a change in wavelength. For example, when light waves pass from air into water, they slow down and bend towards the normal (an imaginary line perpendicular to the surface), which can be visualized when looking at a straw in a glass of water; the straw appears bent at the water's surface. This phenomenon aligns with option A) which accurately describes refraction as the wave bending and changing speed upon entering a new medium.
Other interactions such as reflection, which is described in option B) and is exemplified by seeing oneself in a mirror, involve waves bouncing off a surface without entering a new medium. Diffraction, mentioned in option C), involves the bending of waves around obstacles or through openings, and the Doppler effect, as described in option D), refers to the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source, like the pitch change of an ambulance siren as it moves towards or away from you.
The correct answer to refraction is illustrated by the behavior of waves when they travel from deep to shallow water in a swimming pool, bending toward the normal, slowing down, and shortening in wavelength. Refraction is distinct from reflection, diffraction, and the Doppler effect, as it specifically involves the change in a wave's speed and direction due to entering a different medium, as governed by Snell's law.