Wave Interactions
Middle School
Definition
The ways waves behave when they meet a boundary or obstacle, including reflection (bouncing back), refraction (bending as they change speed), and diffraction (spreading around edges). These interactions explain effects such as echoes and rainbows.
Worked examples
A light ray traveling from air into water bends toward the normal line.
Refraction occurs because light slows down in water, changing direction at the boundary.
Sound waves bounce off a canyon wall and return as an echo.
Reflection happens when waves hit a barrier and bounce back toward the source.
Water waves passing through a harbor opening spread into the calm area beyond.
Diffraction causes waves to bend and spread around edges and through gaps.
Common mistakes
- Refraction only happens with light waves. → Refraction occurs with all wave types when they change speed at a boundary. Sound, water, and seismic waves also refract when entering different media.
- Waves that reflect always bounce straight back in the same direction they came from. → Waves reflect at an angle equal to their incoming angle relative to the surface. The angle of incidence equals the angle of reflection for all wave types.
- Diffraction makes waves stronger. → Diffraction spreads waves around obstacles; it doesn't increase their energy. Energy spreads over a wider area, so intensity typically decreases.
Where you'll use it next
Wave interactions explain how lenses and mirrors work in optics, how seismic waves help map Earth's interior, and how engineers design concert halls and noise barriers using reflection and diffraction principles.
See also
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026