Page 372 Reflection, Refraction, and Diffraction Waves can and do meet boundaries in their medium. When a wave meets a boundary, it can be reflected or transmitted. Reflection can be partial or complete. A wave entering a medium at an angle will change direction.
Diffraction depends on the size of the object relative to the wavelength of the wave.
All these phenomena apply to electromagnetic waves, such as light waves, as well as to pressure waves and water waves.