Touch your throat while you talk, and you feel it tremble. Every sound begins with something that vibrates. Here we see how a vibration makes a sound wave, why the wave needs a material to travel in, and how to find the distance of a lightning flash from the sound of its thunder.
3 lessons, about 1 h 10 min3 simulations10 problems6 practice questionsPython in every lesson
Every sound is made by something that vibrates: it moves quickly to and fro about one place. The faster the vibration, the higher the sound, and the bigger the swing, the louder it is.
Sound travels through a material, called the medium, as a wave of compressions and rarefactions. It cannot cross a vacuum. Sound is a longitudinal wave: the particles vibrate along the direction it travels.
The speed of sound is the distance it travels in one second: about 340 m/s in air, more in liquids and most in solids. It grows a little as the air gets warmer, so we see lightning before we hear the thunder.
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