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10. Sound Waves eLearn.Punjab

Key Points

• In transverse waves particles of the medium vibrate at right angle to the path of the wave.
In a longitudinal wave, particles of the medium vibrate back and forth, parallel to the path of
the wave.

• Sound waves are longitudinal waves.
• Wavelength of a sound wave is the distance between two adjacent compressions or

rarefactions. It is measured in metres (m).
• Frequency is the number of vibrations produced by a vibrating body in one second. It is

measured in hertz (Hz).
• Amplitude of a wave is the maximum distance the wave vibrates from its rest position. It is

also measured in metres (m).
• Pitch and loudness are the characteristics on which sound depends.
• A healthy human ear can hear sounds of frequencies from about 20Hz to 20,000Hz. Different

animals have different audible frequency ranges.
• We use doorbells, sirens, telephones, alarms, stereo players, etc. that produce different

sounds.

Questions

1. Complete each of the following sentences by writing the correct term.
i. The lower portion of a transverse wave ________
ii. The Shrillness or graveness of a sound ________
iii. The distance a wave covers in one second ________
iv. A compression and a rarefaction combine to form ________
v. A material thing through which a wave travels ________
3. Give short answers.
i. Sketch a transverse wave and label a crest, a trough, a wavelength, and amplitude.
ii. Define the wavelength of a longitudinal wave.
iii. Name a few devices that use different sounds in our everyday life.
iv. What makes some sounds louder than others?
v. What is the relationship between frequency and pitch?
vi. How does sound travel?
4. Compare transverse waves and longitudinal waves.
5. What type of waves are sound waves, and how do they transfer sound energy?

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