Monday, January 24, 2011

Sound waves

1. What is sound?

Sound is a form of energy propagated as waves that make our eardrums vibrate.
Sound waves are caused by vibrating objects.
Sound waves are longitudinal waves.

2. How is sound produced by a vibrating objects?

Sound waves are produced when a vibrating object causes the air molecules around it to vibrate.
When a tuning fork vibrates, layers of air vibrate and the sound energy is propagated through the air around it in the form of waves.
When the tuning fork moves forwards, the air is compressed.
When the tuning fork moves backwards, the air layers are pulled apart and cause a rarefaction.
Therefore, a series of compression and rarefactions will produce sound.

3.Why does sound waves is a longitudinal waves?

The air particles vibrate backward and forward in the direction parallel to the direction of propagation of the sound wave.

4. Explain how the loudness relates to amplitude

The loudness of the sound depends on its amplitude.
If the amplitude is increased, the loudness increases.

5. Explain how the pitch relates to frequency

A high pitch sound corresponds to a high frequency and a low pitch sound corresponds to a low frequency of vibration.


The reflection of sound is called echoes.

i) Ultrasound waves (higher than 20 000 Hz) is used to scan and capture the image of a fetus in a mother’s womb.

ii) Sonar is the technique of using ultrasound to locate underwater objects or to measure the depth of a seabed.

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