Ripple tank

Some small ripple tanks fit onto the top of an overhead projector, i.e. they are illuminated from below.

All the basic properties of waves, including reflection, refraction, interference and diffraction, can be demonstrated.

Ripples may be generated by a piece of wood that is suspended above the tank on elastic bands so that it is just touching the surface.

When the rippler is attached with a point spherical ball and lowered so that it just touches the surface of the water, circular waves will be produced.

If a concave parabolic obstacle is used, a plane wave pulse will converge on a point after reflection.

The speed of a wave in water depends on the depth, so the ripples slow down as they pass over the glass.

The dashed line is the direction that the waves would travel if they had not met the angled piece of glass.

If an obstacle with a small gap is placed in the tank the ripples emerge in an almost semicircular pattern.

A simple ripple tank
Image of plane waves
Ripple tank with a spherical source producing circular waves
Wave wrapping around a small object
Waves that are long relative to the size of an object will wrap around the object.
Shadow caused by large object
Waves that are short in respect to the size of an object will cast a shadow behind the object.
Numerical approximation of diffraction pattern from a slit of width equal to five times the wavelength of an incident plane wave in 3D visualization
Numerical approximation of diffraction pattern from a slit of width equal to wavelength of an incident plane wave in 3D visualization