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Rogue Physicist.  Free resources for physics education © 2006-2016 Dorian Pascoe.  Email: dorian@top-school.co.uk

Most resources are available under a Creative Commons Licence.  Visit our mirror at www.physicsweb.altervista.org

 

 

 

...ultrasound...

 

 

 

Objectives:

 

  
 

 

Waves!

  

 

• Know that ultrasound waves are longitudinal waves, with frequencies above the range of human hearing.

 

 

• Know that ultrasound waves are used for a variety of purposes, including medical imaging and industrial applications.

 

 

• Be able to explain in detail how ultrasound waves are used in fish-finders and to obtain medical images.

 

 

  

 

 

 

 

 

 

 

Task 1 - Starter

 

  
 

 

I know the answer!

 

 

  

 

Find someone who knows:

 

 

1) the definition of a transverse wave.

2) the definition of a longitudinal wave.

3) the main features of transverse waves and longitudinal waves.

4) the units of frequency.

5) the range of frequencies that can be heard by humans.

 

 

Your teacher will tell you which questions to discuss.

  

 

 

 

 

 

 

Task 2 - Uses of ultrasound waves

 

  
 

 

Lots of waves!

 

 

 

  

 

Ultrasound waves have frequencies of more than 20kHz, which is outside the range of human hearing.

 

 

 

 

The speaker is oscillating, and a wave propagating from the speaker, but we can no longer hear it.

 

 

Discuss with the person next to you:

 

• any medical uses of ultrasound that you know about.

 

 

• any industrial or home uses of ultrasound that you know about.

 

 

 

 

Your teacher may write some of your ideas on the board.

 

  

 

 

 

 

 

 

 

 

Task 3a - Uses of ultrasound: finding fish

 

  
 

 

 

  

 

This simple animation shows how a fish finder uses ultrasound waves to find shoals of fish.

 

Can you explain how it works?  Use the following words in your explanation:

 

transmitter         pulse         ultrasound         travels         reflect          returns          time         receiver         detect         distance     

 

 

  

 

 

 

 

 

 

 

Task 3b - Uses of ultrasound: medical imaging

 

  
 

 

 

 

  

 

Medical images can also be obtained using ultrasound.  This is used to obtain images of unborn babies, as well as images of internal organs and soft tissues.

 

 

 

This works in the same way as the fish finder, above.  The pulses take different times to return, due to the different distances.  Each time measurement is represented by a shade of grey.

 

 

High resolution ultrasound images of an unborn baby.

 

Write a detailed explanation of how an ultrasound measurement is obtained.  Try to use the following words in your explanation:

 

transmitter         pulse         ultrasound         travels          reflect          medium          density          returns          time         receiver         detect         distance          image          pixel          shade          value

 

  

 

 

 

 

 

 

 

 

 

Homework

 

  
 

 

Let's catch some waves!

 

  

 

No homework task for this lesson.

 

 

Homework task coming soon!