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Name: Marliz C.
Status: student
Age: 8
Location: N/A
Country: N/A
Date: Thursday, April 25, 2002


Question:
How can sound blow out a candle?


Replies:
Marliz,

Sound is "waves" of air wiggling back and forth. It is the back-and-forth wiggling that makes your ear drum vibrate. If you put your hand in front of a loud low-pitched speaker, you can feel the vibrations. If a sound wave is very loud, the air making up the wave moves back and forth a great deal. For a candle, it is almost like being blown back and forth. This is what puts out the flame.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College


Sound is moving oscillation of air from a region of pressure greater than the ambient pressure and a region of pressure less than the ambient pressure. If the frequency, and intensity of the sound is within a certain range the air will oscillate with an amplitude sufficiently large that the candle flame becomes mechanically unstable, or the low pressure is sufficiently small that oxygen is depleted. In either case the candle will extinguish. The ultimate example is if the air motion exceeds the speed of sound and a shock wave results.

Vince Calder



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