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Ripples hit a tilted wall. Which way do they bounce?
Wave Reflection lab · Last updated: 16 October 2026
Straight ripples roll towards a wall set at an angle. You turn the wall and watch where the reflected ripples go. Is there a rule? There is, and it is the same one mirrors follow.
What you'll discover
- Waves bounce off a barrier at the same angle they arrive at.
- Turning the wall turns the reflected waves by twice as much.
- Light, sound and water waves all follow this same law of reflection.
The science in plain words
When a wave hits a barrier it cannot pass through, it bounces back. This is reflection. The direction of the reflected wave follows a simple rule: the angle at which the wave arrives equals the angle at which it leaves.
Scientists measure both angles from an imaginary line standing at right angles to the wall, called the normal. The incoming angle is the angle of incidence and the outgoing angle is the angle of reflection. The law of reflection says they are always equal. Waves that hit the wall head on bounce straight back; waves that arrive at a slant leave at the same slant on the other side of the normal.
Turn the wall by a small angle, and the reflected wave swings round by twice that angle. That is why a tiny tilt of a mirror makes a reflected spot of light jump across a room.
The law works for all waves. It explains mirror images, echoes from a cliff, sonar, and the way curved dishes gather radio waves or sound to a single point.
Where it fits
Common questions
What is the law of reflection?
The angle at which a wave hits a surface equals the angle at which it bounces off, with both angles measured from a line at right angles to the surface, called the normal.
Does sound follow the law of reflection?
Yes. Sound reflects from walls and cliffs just as light reflects from a mirror, which is how echoes and sonar work. Curved surfaces can focus reflected sound in the same way.
Why does a mirror image look reversed?
Light from each point of you reflects straight back off a flat mirror, so the image is front to back reversed. We read that as left and right being swapped.
Related labs
- Sonar & Echolocation: Ping the water and listen. How long until the rock answers?
- Wave Motion: Shake one end of a cord. How fast does the wave run, and how long is each wave?
- Bending Light: Shine a ray into a glass block. How much does it bend?
See all physics labs or every Taz science lab.
Try it yourself
The Wave Reflection lab is one of the interactive 3D science labs inside Taz. Change one thing, predict what will happen, then run it and watch. Labs open after you sign in.