* Refraction: This is the bending of a wave as it passes from one medium to another at an angle. The change in speed causes the wave to change direction. Think of light bending as it enters water, or sound waves changing direction as they pass from air to a solid object.
* Diffraction: This is the spreading of a wave as it passes through an opening or around an obstacle. The amount of diffraction depends on the size of the opening or obstacle relative to the wavelength of the wave.
So, when a wave changes speed as it enters a new medium at an angle, it undergoes refraction, not diffraction. Diffraction occurs when a wave encounters a barrier or opening, causing it to spread out.
