Book 14, Question 120
How Can Sound Waves Clean Eyeglasses?
Sound waves clean eyeglasses in a machine called an ultrasonic cleaner! It is a small tank of soapy water with a device that sends in sound too high to hear. The sound waves make tiny bubbles that scrub away dirt.
More fun facts
- Ultrasonic cleaners use sound to form bubbles in the cleaning liquid.
- The bubbles form and collapse, a process called cavitation, and that makes powerful local forces that clean.
- An ultrasonic transducer changes electrical energy into the ultrasonic vibrations that shake the cleaning liquid.
- Frequencies for ultrasonic cleaning start at 20,000 cycles per second, and industry most often uses 20 to 50 kHz.
- Higher frequencies make smaller cavitation bubbles, so the cleaning action is gentler.
- Ultrasonic cleaning can reach inside the hidden surfaces of complicated parts.
Questions kids ask
Can you hear an ultrasonic cleaner?
Not the ultrasound itself, which is too high for human ears, though the machine may hum or buzz.
Why are ultrasonic cleaners good for jewelry?
The tiny bubbles reach into small cracks and gaps that a brush cannot.