Resonance Bowl

Materials

The materials need for this demonstration are

1 Resonance Bowl

The science behind the Resonance Bowl

Their are two phenomenons that happen in the demonstartion

First the viberation of the reonance bowl causes the bowl to created a sound that is 196 Hz it is created by rubbing your hands against the handles of the bowl

Second thing of it is that in addition, standing waves are created in the water illustrating an interference pattern called a Chladni pattern. Standing waves are produced by the addition of two identical waves traveling simultaneously in opposite directions through any elastic medium. These waves will constructively and destructively interfere with each other as they pass one another. The resulting wave from the addition of these two waves will form a standing wave in the metal rim. The standing wave that is produced sets up FOUR areas of maximum vibration called antinodes, the areas in the water that “spout” and cause the water droplets to jump off the surface. There are also FOUR areas where minimum vibration occurs and these are known as nodes. These nodes show very little water rippling while the antinodes show maximum water rippling. With practice, you should be able to create four antinodes along the entire rim of the bowl that are so strong that the water will spray out of the bowl. This occurs where the artist intentionally engraved the four fish mouths.

The Advanced Physics behind the Resonance Bowl

Your hands are creating vibrations in the handles from the the frictional grip of your wet skin to the brass. As your hands move, this adhesion creates a tension in the skin of your palms, and when this exceeds the frictional forces, your skin will slide, reducing tension. If your hands are in constant motion, your skin will vibrate the handles as it repeatedly sticks and slides. This “Sticking and Sliding” phenomenon is similar to squeaking chalk on a chalkboard, the skidding of tires on pavement or a sneaker squeaking on a gym floor. The vibrating handles will then create transverse mechanical waves to travel outward from the handle along the metal rim of the bowl in BOTH directions. The metal rim acts as an elastic medium to transmit these waves. If the circumference distance around the rim from handle to handle is EQUAL to a multiple of a half wavelengths, then standing waves will be produced. It is easy to create a mechanical wave in the rim with a wavelength exactly equal to the length along the rim from handle to handle. The handles AND the midpoint along the rim BETWEEN the handles will experience minimal vibrations (nodes). There will be four positions around the rim that are nodes, and another four positions that are antinodes. The antinodes will be formed at ¼ and ¾ arc lengths from handle to handle. Nodes will appear at ½ the arc length between handles AND at the handle positions. These positions will be regularly spaced and easily observed from the ripples and disturbances in the water along the edges of the bowl.

Water(up to the demonstrator on how much to put)

also Isopropyl alcohol is necessary

Procedures

1. First place the resonance bowl on a firm surface, that allows the bowl to vibrate

2. Fill half the bowl with clean water it is actually up to the experimenter but this is the most effective amount of water to put in the bowl.

3. Clean the handles with alcohol and rub it from time to time with wool.

4. Wash your hands with soap and do not touch anything other than the handles.

5. Then moiston your hands with water by dipping your hands into the Resonance bowl and then begin rubbing the handles and the water will begin to rise.