Question

Which of the following cannot produce ultrasonics?
(A) Galton whistle
(B) Quartz crystal
(C) Magnetostriction effect
(D) Quincke’s tube

Answer 1

Hint:Ultrasonics are the sound waves of frequency above audible range (i.e.) above 20,000 Hz (or) 20 KHZ. This sound wave is not audible to the human ear, but it exists. There are numerous applications of ultrasonics in engineering and medicine.

Complete step-by-step solution:
Galton's whistle is a type of whistle that emits ultrasonic sound, which most humans cannot hear but which can be heard by some animals, such as dogs and domestic cats, and is used to train them. It is also known as dog whistle.
When pressure or mechanical force is applied along the mechanical axis of crystals such as quartz, tourmaline, Rochelle salt, and others, equal and opposite charges are produced along the crystal's electric axis. This phenomenon is known as piezo-electric effect. This effect can be used in the generation of ultrasonic waves for imaging purposes. Hence, quartz crystals are used to produce ultrasonics.
The magnetostriction effect is the principle of using a magnetostriction oscillator to generate ultrasonic waves. When a ferromagnetic rod such as nickel, iron, or cobalt is subjected to an alternating magnetic field, the rod is thrown into longitudinal vibrations. When the vibrating rod's frequency equals the natural frequency, then resonance occurs. As a result, ultrasonic waves are produced.
Quincke’s tube is an apparatus used to demonstrate the phenomenon of interference and also used to measure velocity of sound in air. It, however, cannot produce ultrasonics.
Hence, Option (D) is correct.
Note:The acronym SONAR stands for Sound Navigation and Ranging. The SONAR principle is based on the ultrasonic echo sounding technique. It is an acoustic technique for locating objects such as submarines or ships or Icebergs in the sea, by sending and receiving a high-frequency sound pulse after that object's reflection.