Section 8.7: Sound Waves

Sound waves are longitudinal waves that propagate through a medium (air, water, solids) due to particle vibrations. The speed of sound depends on the medium and its properties.

\[ v = f \lambda \]

Where:
\( v \) = speed of sound (m/s)
\( f \) = frequency of the sound (Hz)
\( \lambda \) = wavelength (m)

Key concepts:
- Compression and rarefaction regions
- Amplitude related to loudness
- Frequency related to pitch

Example: Wavelength of a Sound

A sound wave has a frequency of 440 Hz. If the speed of sound in air is 343 m/s, find the wavelength.

Wavelength: \( \lambda = \frac{v}{f} = \frac{343}{440} \approx 0.780 \text{ m} \)

Practice Problems

  1. A tuning fork produces a sound of frequency 512 Hz. Find its wavelength in air (v = 343 m/s).
  2. A sound wave has a wavelength of 1.5 m in air. What is its frequency?
  3. Explain why the speed of sound is higher in solids than in air.
  4. Two sound waves with the same amplitude but different frequencies are heard. Which one has higher pitch?
  5. If a sound source moves toward a stationary listener at 20 m/s and the speed of sound is 343 m/s, describe qualitatively what happens to the perceived frequency.
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