Sound

21.	Which one of the following statements is not correct?
	A. The nature of sound waves in gases is longitudinal
	B. Sound waves of frequency less than 20 Hz are relatively strong.
	C. Sound waves with higher amplitudes are stronger
	D. Sound waves with higher audio frequencies are sharper Option”B” is correct

22.	Which of the following type of wave is used in night equipment
	A. Radio waves
	B. Microwave
	C. Infrared wave
	D. None of the above Option “C” is correct. Infra-red waves are used in night vision apparatus as these are very low energy radiation waves which are available below red rays on the visible spectrum

23.	In which one of the following the speed of sound is maximum
	A. gases
	B. vacuum
	C. liquids
	D. solids Option “D” is correct. Sound is a longitudinal wave. It propagates by vibrating the particles present in the medium. So the speed of sound depends on the density of the medium through which the sound wave is travelling. The speed of the sound is directly proportional to the density of the medium Since the density of the solid is greater than the density of liquid, gas and vacuum. So the speed of the sound is maximum in solid.

24.	A jet plane flies through air with a velocity of 2 Mach. While the velocity of sound is 332 m/s the airspeed of the plane is:
	A. 166 m/s
	B. 66.4m/s
	C. 332 m/s
	D. 664 m/s Option “D” is correct.

25.	In which medium the speed of sound will be maximum at a temperature of about 20°C?
	A. Air
	B. Granite
	C. Water
	D. Iron Option “D” is correct.

26.	A bio-method in which ultrasonic sound is used___
	A. Sonography
	B. ECG
	C. ECG
	D. X-ray Option”A” is correct. An ultrasound scan is a medical procedure that captures live images from within the body using high-frequency sound waves. Sonography is another name for it. The Ultrasonic sound has a frequency higher than 20000Hz. Ultrasound is sound waves with frequencies higher than the audible frequency. Humans cannot hear Ultrasonic sounds. Ultrasonic devices are used to detect objects and measure distances. Ultrasound imaging or sonography is often used in medicine. The frequency of audible sounds is usually 20-20,000 hertz

27.	Which waves cannot propagate in vacuum?
	A. Light
	B. Heat
	C. Sound
	D. Electromagnetic Option “C” is correct. Sound waves cannot propagate through a vacuum because sound waves are . Light waves can propagate through a vacuum because light waves are electromagnetic waves.

28.	While shouting people always keep the palm near the mouth because-
	A. In that case the sound energy would point in only one direction
	B. Sound fullness increases of sound
	C. Pitch of voice increases
	D. This action has no effect on the sound Option “A” is correct. When we have to shout aloud to someone at a distance we cup our hands around our mouth so that all the sound propagates in one direction without spreading out.

29.	Sound waves cannot travel___
	A. In solid medium
	B. In liquid medium
	C. In gaseous medium
	D. In a vacuum Option”D” is correct. Sound cannot travel through a vacuum. A vacuum is an area without any air, like space. So sound cannot travel through space because there is no matter for the vibrations to work in. Sound waves need to travel through a medium such as a solid, liquid, or gas.

30.	What is the instrument used for detecting and rectification of sound waves called?
	A. Radar
	B. Sonar
	C. Call
	D. None of the above Option “B” is correct. SONAR- Sound Navigation And Ranging

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