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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
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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
Here
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 .
Questions
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?
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?
NCERT Question 18 - How is ultrasound used for cleaning?
NCERT Question 19 - Explain the working and application of a sonar.
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
NCERT Question 21 - Explain how defects in a metal block can be detected using ultrasound.
