A sound wave passes through air. At point P the air particles are crowded close together…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A sound wave passes through air. At point P the air particles are crowded close together. At point Q they are spread far apart.
- Which point is a compression, and which is a rarefaction?
- Where is the pressure higher?
- P and the next point like P are apart. What is this distance called, and how far is P from the nearest point like Q?
Need a reminder? The key ideaShow
Every sound is made by a vibration. Sound needs a medium and cannot cross a vacuum. It is a longitudinal wave: the particles vibrate along the direction of travel, making compressions (high pressure) and rarefactions (low pressure).
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) P is a compression; Q is a rarefaction.
Step 2. (b) At P: crowded particles push harder.
Step 3. (c) Compression to compression is one wavelength, . Compression to the next rarefaction is half of it: .
Answer: P compression, Q rarefaction; higher at P; the wavelength, and .
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