Wave Effects

Overview

This lesson moves from wave vocabulary to wave behaviour. Keep every explanation tied to a wavefront diagram so you can see what changes at a boundary and what stays the same.

What You Need to Know

• Show reflection at a plane barrier using parallel wavefronts and a normal line.
• Model refraction as a change in speed that changes wavelength when water depth changes.
• Use narrow gaps and edges in a ripple tank to show diffraction clearly.
• Compare large and small gaps against the same wavelength so you can judge when spreading is greatest.

How to Work Through It

1. Start with a retrieval task on wavelength, frequency, and wave speed so you can describe what they see in the ripple tank accurately.
2. Demonstrate reflection and refraction in the ripple tank, pausing to sketch the matching wavefront diagrams with you.
3. Compare diffraction through different gap widths and around an edge, then check whether you can predict the pattern before each demonstration.
4. End with short explanation questions where you justify the pattern rather than only naming the effect.

Check Your Understanding

• Ask which quantities change when waves enter shallower water: speed, wavelength, frequency, or all three.
• Use a quick comparison task where you rank three gaps by the amount of diffraction for the same wavelength.

Common Mistakes

• Thinking refraction happens because waves hit a boundary rather than because their speed changes. Keep returning to the change in depth and wavefront spacing.
• Many assume the narrowest gap always gives the biggest pattern without relating it to wavelength. Use side-by-side diagrams with the same wavelength.
• Diffraction is sometimes treated as only a gap effect. Include diffraction at an edge explicitly.

Next Steps

• Set annotated wavefront diagrams for reflection, refraction, and diffraction as the main homework.
• Carry forward the language of longitudinal versus transverse waves, because the next lesson applies it to sound.