Purpose: This experiment is an investigation of how sound waves transmit energy from one glass to another. The experiment will also demonstrate how natural frequency and resonance relate to one another. For more information on sound waves see Sound for Kids.
- 2 identical glasses
- pitcher of water or a glass measuring cup
- 1 thin piece of wire (1/2" longer than the diameter of the glasses)
- Fill the pitcher or measuring cup with water.
- Pour equal amounts of water into each glass.
- Bend down the edges of the wire ends carefully so there is 1/4 inch on either side to hold the wire in place.
- Place the wire across the top of one glass in the center.
- Gently rub around the rim of the other glass with the tip of your finger.
- Make observations. Focus on the actions of the glass with the wire on it.
- Experiment with different (equal) water levels in the glasses. What do you notice?
- Experiment with unequal water levels in the glasses.
What do you think the term natural frequency means now that you have conducted the experiment?
*Frequency is the number of sound vibrations per second.
Define resonance using the following terms: reflection, vibration, and identical objects.
The glass that is rubbed sends out a vibration that is picked up (absorbed) by the second glass. Because the glasses have the same amount of water and are the same type of glass, they have the same natural frequencies. The sound wave transmits energy to the glass, causing a vibration, which is then carried to the wire, causing it to move.
Reference: NASA SciFiles
More Sound Experiments:
Sound Pitch - Learn how frequency effects sound and pitch.
Sound Vibrations- Learn about sound by making a kazoo.
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