Write short notes on SONAR.

Hint: SONAR is a navigational method that makes use of sound propagation. SONAR can also be used to track remote objects as well as communicate with other things.

Complete step by step solution:
SONAR is a device that detects distances in the ocean or locates sunk ships or other missing objects by using high frequencies and high-intensity sound waves. SONAR can be used for a variety of underwater purposes, including submarine communication and navigation.

Sound Navigation and Ranging is the full form of SONAR. The principle of echoes is used in sonar. A powerful and short (ultrasonic) sound signal is sent to the ocean's bottom. It then detects the echo of this signal.

There are two kinds of SONAR technology:
Active SONAR: this involves the emission of sound waves and waiting for the echo to come back.
Passive SONAR: this is used to listen to the sounds made by underwater objects.

For underwater communications, ships and submarines use special sonars. Sonar is used in medical imaging to detect cysts and cancer cells, and this process is known as a sonogram. The military uses it to track enemy warships and submarines.

Note:
> Leonardo da Vinci was the first to introduce the idea of SONAR when he inserted a tube into the water to listen to the sounds produced by various vessels.
> Active SONAR has been linked to mass extinctions of marine mammals, according to research. The most frequent victim of extinctions is beaked whales. They are highly vulnerable to mid-frequency active SONAR.