PURPOSE: To demonstrate the properties of diffraction and interference with water waves.
DESCRIPTION: A mechanical vibrator generates a series of traveling periodic plane wavefronts. The wavefronts pass through a single slit to show diffraction. The single slit can be changed to a double slit to show two slit interfernce.
The ripple tank consists of a shallow water tank supported above a 45 degree mirror. A point source of light illuminates the shadow of the water waves. The wave image reflects off a diagonal mirror and the image is cast onto a ground glass screen. The image appears as shown in the photo above. Each water wave acts much like a curved lens. The crest of the wave is seen as a bright region and the the trough is seen as a dark region.
Inside the ripple tank is a mechanical vibrator attached to a paddle that produces either point wavelets or parallel wavefronts. Various obstructions and barriers can be inserted into the path of the wave, such as a single slit, a double slit or an edge. The assembled ripple tank is shown in the photo at right.
EQUIPMENT: Ripple tank set up, as photographed.
SETUP NOTES:
Updated by Jerry Zani in 4/11/2000