SONAR stands for
- A.Sonographic Natural Ranging
- B.Simple Operational Navigation Ranging
- C.Sound Navigation and Ranging
- D.Simple Operational Natural Ranging
Correct answer
Explanation
The correct answer is C, Sound Navigation and Ranging. SONAR uses sound waves under water to find the distance and direction of objects.
A SONAR set on a ship has a transmitter that sends out pulses of ultrasound and a detector that picks up their echo from the sea bed, a shoal of fish, a wreck or a submarine. Measuring the time t for the echo to return and knowing the speed of sound in sea water v (about 1,500 m/s), the distance is d = v × t ÷ 2, halved because the sound travels there and back. Ultrasound is used because its short waves travel far in water without spreading much. Bats and dolphins use the same echo principle.
A is wrong because sonography is ultrasound imaging of the body, and the word is not part of the acronym.
B is wrong because the S stands for sound, not simple, and there is no operational in it.
D is wrong because it repeats the same made-up words and drops navigation.
Exam tip: SONAR – sound under water; RADAR – Radio Detection and Ranging; distance = speed × time ÷ 2.
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