Ultrasound

Question 1

what is ultrasound

Answer 1

sound with a frequency greater than 20,000 hz

Question 2

how is the distance between a ship and the seabed figured out with ultrasound

Answer 2

• pulse of sonar is shot from the ship to the seabed
• the echo of it is detected
• time taken for the echo to travel back to the ship / 2 (with the speed of ultrasound in water known) allows them to calculate the depth of seabed

Question 3

explain how ultrasound is used in foetal scanning

Answer 3

• ultrasound is shot at the foetus with an ultrasound transmitter
• when it reaches a boundary between 2 different media
• like the fluid in womb and skin of foetus
• some of the wave is reflected back
• exact timing and distribution of echoes are processed by a computer to produce a video image

Question 4

how is ultrasound used in the body for scanning

Answer 4

• ultrasound shot at person
• between 2 different media some of it is reflected back and processed by a computer (echoes)
• a video image is shown

Question 5

what is infrasound

Answer 5

sound with a frequency lower than 20hz

Question 6

what are the 2 reasons gel used for foetal scanning

Answer 6

to allow the waves to directly transmit to the tissue beneath and to reduce static

Question 7

process of how the ear processes sound

Answer 7

• sound wave enters canal
• sound makes eardrum vibrate
• tiny bones amplify vibrations
• passed to liquid inside cochlea
• hairs detect vibrations and create impulses
• impulse travels to brain through sensory neurons (auditory nerves)

Question 8

what happens to a wave when it passes from one medium into another

Answer 8

• some of the wave is reflected off the boundary between the two media
• some is transmitted and refracted (partial reflection)

Question 9

how is the way a wave reacts when passing through two media used with pulses

Answer 9

• you can point a short burst of ultrasound at an object

- wherever there are boundaries between one substance and another, some ultrasound gets reflected back

Question 10

how can you measure how fat away a boundary is when using ultrasound

Answer 10

the time it takes for the reflections to reach a detector

Question 11

how are pulses used in foetal scanning

Answer 11

• ultrasound waves passed through the body
• when they reach a boundary between 2 media
• like fluid in the womb or skin of foetus
• some of the wave is reflected back and detected

Question 12

what type of image is produced in foetal scanning and how does the computer do it

Answer 12

• time taken and distribution of the echoes are processed by a computer
• produces a video image of the foetus

Question 13

what can the waves reflected back from foetal scanning also be called

Answer 13

echoes

Question 14

what do we know about ultrasound imaging in terms of its safety

Answer 14

as far as we know, its completely safe

Question 15

what is ultrasound used in

Answer 15

• medical imaging like pre-natal scanning of foetus
• industrial imaging like finding flaws in amterials
• echo sounding

Question 16

how are ultrasound waves entering a material usually reflected

Answer 16

• by the far side of the material

- meaning the wave travels all the way to the back and is reflected from there

Question 17

how are ultrasound waves reflected if there is a flaw in a material, like a crack and why

Answer 17

• the waves will be reflected sooner

- because the waves reflect off the flaw which would be closer to the first boundary then the far back side

Question 18

what do the ways in which ultrasound waves are reflected in materials depending on their quality cause ultrasounds to be used for

Answer 18

• they can be used to find flaws in objects

- such as pipes, wood or metal

Question 19

what is echo sounding

Answer 19

• a type of sonar used by boats and submarines

- to find out the distance to the seabed or to locate objects in deep water