1. To know how ultra sound works and how it compares to x-rays.
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Physics 3
Ultrasound
To know how ultra sound works and how it compares to x-rays.

2. 26/04/2017

3. How sound travels…
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As we know, sound waves are formed when something vibrates. But how does the sound reach our ears?
Air molecules
2) The vibrations pass through air by making air molecules vibrate
3) These vibrations are picked up by the ear
1) An object makes a sound by vibrating

4. Sound can be reflected and refracted
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An Echo is a reflected sound wave
Echolocation is also used in the shipping industry but remember
Sound in air = 330m/s
Sound in water = 1500m/s
Bats use echoes to locate insects. They time how long the echo takes to come back and use that to locate the insect

5. Using an oscilloscope 1) Quiet sound, low frequency:
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1) Quiet sound, low frequency:
2) Quiet sound, high frequency:
3) Loud sound, low frequency:
4) Loud sound, high frequency:

6. Ultrasound
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Ultrasound is the region of sound above 20,000Hz – it can’t be heard by humans. There are a number of uses for ultrasound:
Pre-natal scanning
Cleaning – it can be used to dislodge dirt
Detecting flaws or cracks
Medical treatment

7. How does ultrasound work?
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Ultrasonic waves are partly _________ at the boundary as they pass from one _______ to another. The time taken for these reflections can be used to measure the _______ of the reflecting surface and this information is used to build up a __________ of the object.
Words – depth, reflected, picture, medium

8. Kerboodle Animation
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millepau

9. Speed Calculation
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Distance travelled = speed of ultra by pulse sound waves in X transit time body tissue s (m) = v (m/s) x t (s) However, the depth of the boundary is only half of the distance travelled: Distance to boundary = speed of ultrasound waves X transit time

10. Calculating the speed of sound
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We can work out how far away surfaces are using ultrasound by connecting the transducer to an oscilloscope and measuring the transit time of each pulse.
This is the time taken by the pulse to travel from the transmitter to and from the boundary that reflected it.

11. Using an oscilloscope with ultrasound
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Consider a block of metal with a flaw:
20ms/div
Q. If the speed of the ultrasonic wave is 3,000m/s how far away is the flaw from the detector?

12. X-Rays Vs Ultrasound
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Evaluate the advantages and disadvantages of using ultrasound and x-rays (4 marks)
Ultrasound
Non-ionising, harmless when scanning
Reflected at boundaries between different tissue types so they can be used to scan different organs and soft tissues.
X-Rays
Highlight deformities/breaks in bones, can be used in cancer treatment

13. Opinions on investment in pre natel scans: Kerboodle
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Opinions on investment in pre natel scans:
Kerboodle