Balloons filled with helium, CO2, or SF6 act as diverging and converging lenses, respectively.
What it shows:
A balloon, filled with a gas different from air, will refract sound waves. A gas denser than air turns the balloon into a converging lens and a lighter gas makes it a diverging lens. An air-filled balloon has little effect.
How it works:
The refraction phenomenon occurs whenever waves travel from one medium to another in which the velocity of the wave changes. The amount of refraction at...
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