Ripple Tank: Single and Double Slit Diffraction and Interference (C31) [3B50.20]
Why Physics Stack Exchange recommends it
Physics Stack Exchange answerers and commenters point people to it as a clear visual demonstration of Huygens-Fresnel wavefronts, slit diffraction and interference using water waves.
Recommended by 2 people across 2 different months, 2016 to 2024.
What it is
A short MIT Physics Instructional Resources Lab demonstration using a ripple tank, where a vibrating bar sends plane water waves at a barrier with an adjustable opening. A narrow slit produces circular waves on the far side, while a wider slit shows interference patterns, illustrating the Huygens-Fresnel principle.
What people said
Recommends Floris · 2016-01 · Physics Stack Exchange · on “Is Huygens-Fresnel principle applicable for waves other than light?”
The principle that every point on a wavefront can be thought of as an emitter of spherical (or, in 2D, circular) waves is applicable to any waves - see any introductory high school course on waves, where the demonstrations are typically done with water surface waves. Note that, as @ignacio pointed out, the construction is only exact in odd dimensions (in practice that means 3D), but even in 2D it is quite convincing: Nice demonstration with water waves in 2D [this video] And the link given by Ignacio: Mathematical proof that Huygens construction is only valid in odd dimensions [LINK]
Recommends Floris · 2016-01 · Physics Stack Exchange · on “Is Huygens-Fresnel principle applicable for waves other than light?”
Mechanical transverse waves are restricted to 1D or 2D and expand in circular waves as I stated. See this nice MIT demo [this video]
Recommends anna v · 2016-10 · Physics Stack Exchange · on “What actually causes light to diffract when encountering a slit?”
The light, when closely encountering the matter in the slit is 'bent' or rather changes direction and explained as an interference between the light wave and the matter Classically light is an electromagnetic wave; it is simple to understand waves when seen in water, for example [this video] . The sides of the slit are a boundary that force the wave to change direction and generate interferences because of the structure of what a wave is. It is the same with water as in the video , the classical view describes light waves too. which also has wave-like properties. Wave like properties of the boundaries do not affect classical water waves because the scale of a water wave and the scale of the quant
Cites Albatross · 2024-01 · Physics Stack Exchange · on “Interference in single slit”
@PhysicsDave I would not agree that it's questionable. The examples in my comment above would support my assertion, as would the video demonstration (and this one [this video] and this one [LINK] ). I don't know why you are so sure that the straightforward mathematics which predicts the characteristic diffraction/interference pattern somehow fails to apply for water waves.
Cites Andrew Cheong · 2024-08 · Physics Stack Exchange · on “Would the angle of diffraction past a slit be different for water versus a different liquid compound?”
I see, thank you. To test my understanding, first I reviewed single-slit interference for light [LINK] —I hope this is still correct. Then I looked for purported single-slit interference in water, _e.g._ this video [this video] —so you are saying the "interference" that seems to appear around 1m30s is actually due to reflections and anomalies, yes?