6. Sound Waves

Question 1

Sound

What it is + How it is produced

Answer 1

Sound is a longitudinal wave (direction of vibration is parallel to the direction of wave propagation) produced by a vibrating source:

• Cannot travel through a vacuum
• Needs a medium to propagate (fastest in solid, slowest in gas)
• Medium particles are not transported away from the source

Question 2

How is sound propagated?

Answer 2

The forward and backward vibration of a source is passed on to the air/water particles. This causes alternate regions of the air particles to be compressed and extended, resulting in a series of compressions and rarefactions.

• Compressed regions are called compressions (higher pressure)
• Extended regions are called rarefactions (lower pressure)

Question 3

Wavelength of Longitudinal Wave

Definition

Answer 3

The wavelength of a longitudinal wave is the distance between the centres of two successive compressions or rarefactions

Question 4

Pitch of sound is affected by

Answer 4

Frequency of the sound wave

Question 5

Loudness of sound is affected by

Answer 5

Amplitude of the sound wave

Question 6

Ultrasound is used in

Answer 6

1. Sonar (Sound Navigation And Ranging)

• Strength of reflected pulse depends on distance and characteristics of reflecting objects

2. Imaging Internal organs

• Strength, direction, timing of reflected pulse are measured to allow the reflecting surface to be mapped

3. Pre-natal scanning
4. Breaking up kidney stones
5. Cancer treatment