iv. Ultrasonic Waves: Cleaning, Imaging, and Sonar Applications

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Ultrasound and Its Applications: Cleaning, Imaging, and Medical Applications

Ultrasounds are high frequency waves.
- They are able to travel along well defined paths even in the presence of obstacles.
- Ultrasounds are used extensively in industries and for medical purposes.
It is used to clean parts located in hard-to-reach places, for example, spiral tubes, odd shaped parts, electronic components, etc.
- Objects to be cleaned are placed in a cleaning solution and ultrasonic waves are sent into the solution.
- Due to the high frequency, the particles of dust, grease and dirt get detached and drop out.
It can be used to detect cracks and flaws in metal blocks in construction of big structures like buildings, bridges, machines and also scientific equipment.
- Ultrasonic waves are allowed to pass through the metal block and detectors are used to detect the transmitted waves.
- If there is even a small defect, the ultrasound gets reflected back indicating the presence of the flaw or defect.

Ultrasonic waves are made to reflect from various parts of the heart and form the image of the heart.
- This technique is called ‘echocardiography’.
Ultrasound scanner is an instrument which uses ultrasonic waves for getting images of internal organs of the human body.
- It helps the doctor to detect abnormalities, such as stones in the gall bladder and kidney or tumours in different organs.
- In this technique the ultrasonic waves travel through the tissues of the body and get reflected from a region where there is a change of tissue density.
- Ultrasonography is then used to generate images of the organ.
Ultrasonography is also used for examination of the foetus during pregnancy to detect congenital defects and growth abnormalities.
- Ultrasound may be employed to break small ‘stones’ formed in the kidneys into fine grains. These grains later get flushed out with urine.

Sonar: Depths with Ultrasonic Waves

About Sonar: The acronym SONAR stands for Sound Navigation And Ranging.
- Use Ultrasonic Waves: Sonar is a device that uses ultrasonic waves to measure the distance, direction and speed of underwater objects.

Consisting Objects and Functioning: Transmitter, Detector, and Underwater Functioning

It consists of a transmitter and a detector and is installed in a boat or a ship.
The transmitter produces and transmits ultrasonic waves.
These waves travel through water and after striking the object on the seabed, get reflected back and are sensed by the detector.
The detector converts the ultrasonic waves into electrical signals which are appropriately interpreted.
Calculating Distance: Calculating Depths with Underwater Sonar

The distance of the object that reflected the sound wave can be calculated by knowing the speed of sound in water and the time interval between transmission and reception of the ultrasound.
Let the time interval between transmission and reception of ultrasound signal be t and the speed of sound through seawater be v.
The total distance, 2d travelled by the ultrasound is then, 2d = v × t.
The above method is called echo-ranging.

Application: The sonar technique is used to determine the depth of the sea and to locate underwater hills, valleys, submarines, icebergs, sunken ships etc.