demonstrations:strobe_light_ripple_tank
Strobe Light Ripple Tank
Materials: ★★★ Requires materials not commonly found in school laboratories
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★☆ Some safety precautions required to perform safely
Categories: Electromagnetic Spectrum and Waves, Light, Motion
Alternative titles:
Summary
A shallow tank of water is used with a vibrating wave source and a strobe light to create frozen images of water waves, allowing clear observation of reflection, refraction, diffraction, and interference.
Procedure
- Fill the ripple tank with a shallow, even layer of water.
- Place the wave generator so it just touches the surface of the water.
- Turn on the wave generator to produce regular water waves.
- Switch on the strobe light and adjust its frequency until the waves appear stationary.
- Insert barriers, gaps, or shaped objects into the tank to demonstrate reflection and diffraction.
- Change water depth in part of the tank to demonstrate refraction.
- Use two wave sources to show interference patterns.
Links
Strobe Ripple Tank - VITTA Education:
Variations
- Use a phone strobe app instead of a laboratory strobe light.
- Use different wave frequencies to change wavelength and spacing.
- Adjust the strobe frequency slightly to show slow motion wave movement.
- Add curved barriers to demonstrate focusing and spreading of waves.
Safety Precautions
- Ensure electrical components are kept away from water spills.
- Dry hands before adjusting electrical controls.
- Avoid looking directly into bright strobe lights for extended periods.
- Mop up any spilled water immediately to prevent slipping.
Questions to Consider
- Why do the waves appear to stop moving when the strobe frequency matches the wave frequency? (The strobe flashes illuminate the waves at the same point in each cycle.)
- How does changing water depth affect wave speed? (Waves travel more slowly in shallower water.)
- What causes the pattern seen in wave interference? (Constructive and destructive interference between overlapping waves.)
- How is diffraction affected by the size of the gap compared to the wavelength? (Diffraction is strongest when the gap is similar in size to the wavelength.)
