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📘 Lesson 2 of 7 · Waves

🔊 Sound Waves

Sound is a longitudinal mechanical wave created by vibrating objects, traveling through air (or other media) as a series of compressions and rarefactions.

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01 Key Concepts

How Sound is Produced

A vibrating object (like a speaker cone or vocal cords) pushes and pulls on nearby air molecules, creating alternating regions of compression (high pressure) and rarefaction (low pressure).

Speed of Sound

Sound travels at approximately 343 m/s in air at room temperature; it travels faster through denser media like water or solids.

Pitch and Loudness

Pitch corresponds to frequency (higher frequency = higher pitch); loudness corresponds to amplitude (larger amplitude = louder sound).

The Decibel Scale

A logarithmic scale used to measure sound intensity, because the human ear can detect an enormous range of sound intensities.

Sound Cannot Travel Through a Vacuum

Since sound is a mechanical wave, it requires a medium (like air, water, or a solid) to propagate -- famously, 'in space, no one can hear you scream'.

02 Key Formulas

03 Solved Examples

Example 1 A sound wave has frequency 440 Hz (a musical note A) and travels at 343 m/s. Find its wavelength.
  1. Apply lambda = v/f = 343/440.
Answer: Approximately 0.78 meters
Example 2 Why can astronauts not hear each other speak directly in the vacuum of space?
  1. Sound requires a medium (like air) to travel through, since it's a mechanical wave.
  2. The vacuum of space has no medium to carry sound vibrations.
Answer: Sound cannot travel through a vacuum, since it needs a medium to propagate
Example 3 Why does sound travel faster through steel than through air?
  1. Sound speed depends on how tightly packed and strongly connected the medium's particles are.
  2. Steel's particles are much more tightly bound than air molecules, transmitting vibrations more quickly.
Answer: Denser, more rigid media transmit sound vibrations faster than less dense media like air

04 Practice Questions

1A sound wave has frequency 220 Hz, speed 343 m/s. Find wavelength.
343/220≈1.56m
2What does a higher frequency sound wave correspond to?
Higher pitch
3What does a larger amplitude sound wave correspond to?
Louder sound
4Can sound travel through a vacuum?
No
5What scale is used to measure sound intensity?
The decibel scale

📄 Sound Waves — Downloadable Worksheet

10 questions with a full answer key. Grab the PDF to print, or try the interactive version in your browser.

🗒 Cheat Sheet ⬇ Download PDF 🖥 Interactive Worksheet