Ultrasound is used for following purposes

Cleaning Hard to Reach Parts

They are used for cleaning Hard to reach places

Example-Spiral Tube,

Objects are placed in cleaning solution

Ultrasound waves are passed through it

Due to high frequency, dirt and grease get detached and parts get cleaned



Detecting Cracks in Metal Blocks

Metal blocks are used in building bridges,machines etc

Sometimes, these metal blocks look fine from outside but may have cracks inside

To detect it, ultrasound waves are passed

If there is no defect, these ultrasound waves pass through and are detected by detectors

But if there is a defect, these waves reflect back (and hence not detected by detector)



Echocardiography (ECG)

It is used to check heart problem in patients

Ultrasound waves are transmitted on heart

These reflect back forming image of the heart

This is called echocardiography



Breaking Kidney Stones

Sometimes, stones get formed in kidneys of some patients

These are broken down into small grains with the help of ultrasound

So these grains pass out with urine and there is no need of surgical operation



Ultrasound scanners

Doctors use these ultrasound scanners to get image of internal organs of human body

These waves reflect on organs and reflect back where there is change in tissue density

These help in finding image of different organs

They are also used to see foetus (unborn baby) in case of pregnant ladies



Find Distance(SONAR)

SONAR Means Sound Navigation and Ranging

Ultrasound waves are used in case of underwater objects (like submarines)

It is used to find depth of sea

It is also used to locate` underwater hills,valley,submarines etc



What is Sonar technique or Echo Ranging

Parts of SONAR

SONAR Contains

Transmitter-for transmitting ultrasonic waves

Detector-For Detecting Reflected Ultrasonic Waves


How does it work

Transmitter produces ultrasonic waves in sea or river

These waves travel through water,strike an object(example submarine) and are reflected back

These detector converts ultrasonic waves into electric signals


How is Distance Calculated

We know that

Speed = Distance/Time

Speed × Time=Distance

Distance = Speed × Time


Speed is speed of Ultrasonic wave in Water

Time is Distance taken in transmitting and interpreting signal

Note:- This distance is of both sides(sending signal and receiving it back,so to calculate one side distance,we divide it by half)

The above process is called echo-ranging .



Question 1 Page 172 - A submarine emits a sonar pulse, which returns from an underwater cliff in 1.02 s. If the speed of sound in salt water is 1531 m/s, how far away is the cliff?

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Example 12.3 - A ship sends out ultrasound that returns from the seabed and is detected after 3.42 s. If the speed of ultrasound through seawater is 1531 m/s, what is the distance of the seabed from the ship?

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NCERT Question 18 - How is ultrasound used for cleaning?

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NCERT Question 19 - Explain the working and application of a sonar.

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NCERT Question 20 - A sonar device on a submarine sends out a signal and receives an echo 5 s later. Calculate the speed of sound in water if the distance of the object from the submarine is 3625 m

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NCERT Question 21 - Explain how defects in a metal block can be detected using ultrasound.

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CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo