A Homemade Ripple Tank
Proof that great physics doesn’t need expensive equipment
Ripple tanks are a brilliant way to teach wave behaviour — reflection, refraction, diffraction, interference — but commercial ripple tanks are expensive, fragile, and often locked away in cupboards “for special occasions”.
Some of our students want to recreate a ripple tank at home. They are easy to create using
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the clear lid of a “Really Useful Box”
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a few books for the lid to rest on
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a torch
And it works beautifully.
The Simple Setup
What We Use
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Clear plastic lid (flat, rigid, transparent)
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Books to raise the lid off the bench
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Torch or LED light underneath
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White paper or bench surface to project onto
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A dropper, finger, ruler, or vibrating source to create waves
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A shallow layer of water — just a few millimetres
The lid becomes the water surface, the books provide clearance for light, and the torch projects wave patterns onto the bench below.
No wiring.
No motors.
No specialist parts.
What Students Can See Instantly
1. Circular Waves
A fingertip tap or dripping water shows clean circular wavefronts spreading out from a point source.
2. Reflection
Place a ruler or straight edge in the water and observe waves reflecting with angle of incidence = angle of reflection.
3. Refraction
Create shallow and deep regions by tilting the lid slightly or adding a submerged object.
Wave speed changes are immediately visible.
4. Diffraction
Two obstacles with a gap between them demonstrate diffraction clearly — even better when the gap is close to the wavelength.
5. Interference
Two wave sources (two fingers or droppers) produce clear constructive and destructive interference patterns.
All of this from a plastic box lid and a torch.
Why This Works So Well for Teaching
Low Cost = High Access
Because it’s cheap, you can:
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let students try it themselves
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repeat experiments without worry
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run it in small groups
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recreate it at home
No “teacher-only” equipment.
Nothing to Break
If the lid scratches or the torch fails, replacements are trivial.
Concepts Over Complexity
Students focus on the physics, not on how the apparatus works.
Perfect for Filming
The projected patterns are ideal for:
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slow-motion video
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time-lapse
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overlays and annotations
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online lessons from the studio
It also makes an excellent visual for social media clips.
Extending the Experiment
With a few extras, the same setup can be used to explore:
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wave speed
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frequency vs spacing
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damping
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superposition
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energy transfer
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analogy with light waves
Add a ruler, stopwatch, or camera — and suddenly you’re doing GCSE and A-Level physics with real data.
The Teaching Message
This experiment reinforces an important lesson for students:
Good science is about ideas, not expensive equipment.
If you understand the principle, you can demonstrate it with whatever you have available.
That’s a powerful message for learners — and teachers.
The Takeaway
A ripple tank doesn’t need motors, strobes or specialist trays.
A clear plastic lid, a torch and a bit of water are enough to reveal some of the most beautiful and important ideas in wave physics.
Simple.
Affordable.
Effective.
Exactly how practical science should be.
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