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

  1. Fill the ripple tank with a shallow, even layer of water.
  2. Place the wave generator so it just touches the surface of the water.
  3. Turn on the wave generator to produce regular water waves.
  4. Switch on the strobe light and adjust its frequency until the waves appear stationary.
  5. Insert barriers, gaps, or shaped objects into the tank to demonstrate reflection and diffraction.
  6. Change water depth in part of the tank to demonstrate refraction.
  7. Use two wave sources to show interference patterns.

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.)