sound (physics)

Question 1

What is sound

Answer 1

• longitudinal wave travelling in a medium, created by a vibrating source
• direction of vibration is parallel of direction of wave travel

Question 2

How is sound propagated

Answer 2

• Forward and backward vibration of a source is passed on to the air particles;
• Causes alternate regions of air particles to be compressed and extended
• Compressed regions: compressions
• Extended regions: rarefactions

Question 3

Does sound need a medium to be transmitted

Answer 3

Yes. Cannot travel through a vacuum. Needs a medium to propagate from one point to another

Question 4

How is frequency related to sound

Answer 4

Higher frequency –> higher pitch

Question 5

How is amplitude related to sound

Answer 5

Higher amplitude –> louder

Question 6

Describe how an echo is formed

Answer 6

An echo is formed when a sound is reflected off a hard, flat surface such as a large wall
Obeys laws of reflection

Question 7

What is ultrasound

Answer 7

Human beings cannot hear at low (infrasound) and high (ultrasound) frequencies
Ultrasound is sound with frequencies above the upper limit of the human range of audibility

Question 8

What are the applications of ultrasound

Answer 8

• Fishing boats use sonar (Sound Navigation And Ranging): Ultrasonic pulse is emitted into water and reflected pulse is obtained –> strength depends of distance and characteristics of reflecting objects (detect fish, measure depth)
• Imaging internal organs: Image is formed based of strength, direction, and timing of the reflected pulses [handheld scanners, kinds of tissues encountered (distance of various layers)]
• Pre-natal scanning: Pulses sent into womb via a transmitter –>
  Images of foetal development obtained (Strength, direction and timing of each reflected pulse are measured to allow the reflecting surface to be mapped out)
• Breaking up kidney stones and cancer treatment: High-intensity focused ultrasound –> Break into smaller pieces so it can be expelled through urine / Js kill the cells
  Safe and non-invasive compared to surgery

Question 9

How are ultrasound waves different from EM waves

Answer 9

• Ultrasound longitudinal, EM transverse
• Ultrasound cnn pass through a vacuum/need a medium
• Ultrasound cnn travel at the speed of light in a vacuum