Sound

51.	The nature of sound waves is__
	A. Transverse
	B. Longitudinal
	C. Progressive
	D. Electromagnetic field Option”B” is correct. Sound waves are longitudinal waves. This means that the propagation of vibration of particles is parallel to the energy wave propagation direction. When the atoms are set in vibration they move back and forth. This continuous back and forth motion results in a high-pressure and a low-pressure region in the medium.

52.	Which of the following statements is true for sound waves
	A. They can be polarized
	B. It can run in a vacuum
	C. Their speed at 0°C is 332 m per second.
	D. All the above statements are true Option “C” is correct.

53.	Infrasonic waves have a frequency of
	A. Less than 20Hz
	B. More than 20 Hz
	C. Over 20,000 Hz
	D. Less than 20 Hz Option “A” is correct. Sound waves of frequency less than 20 Hz which can’t be heard by us are called infrasonic waves.

54.	Ultrasonic waves are those sound waves whose frequency is-
	A. Is between 20 Hz and 1000Hz
	B. Between 1000 Hz and 20000 Hz
	C. Is greater than 20 kHz
	D. Less than 20 Hz Option “C” is correct. Ultrasonic wave is defined as “inaudible sound with high frequency for human” the frequency of which generally exceeds 20 kHz. These days, sound wave which is not intended to be heard is also called ultrasonic wave.

55.	Ultrasonic waves are those waves
	A. to which man can hear
	B. which man can not hear
	C. which are of high velocity
	D. having high amplitude Option “B” is correct.

56.	Who was the first to generate ultrasonic waves by whistling?
	A. Newton
	B. Galton
	C. Hertz
	D. Faraday Option “B” is correct. The Correct Answer is Francis Galton.

57.	Which phenomenon is used by bats or dolphins to detect prey, predators or obstacles?
	A. Refraction of sound
	B. Formation of vibrations
	C. Scattering of sound
	D. Echo location Option “D” is correct. Echolocation, also called biosonar, is the biological sonar used by several kinds of animals. Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects. Echolocating animals include some mammals and a few birds; most notably microchiro-pteran bats and odontocetes (toothed whales and dolphins), but also in simpler form in other groups such as shrews, one genus of megachiropteran bats (Rousettus) and two cave dwelling bird groups, the so-called cave swiftlets in the genus Aerodramus (formerly Collocalia) and the unrelated Oilbird Steatornis caripensis.

58.	_____ is used to drive away insects and harmful elements from homes.
	A. Ultrasonic wave
	B. Radio waves
	C. Infrared wave
	D. Subsonic wave Option “A” is correct

59.	What does the pitch of a sound depend on?
	A. Frequency
	B. Intensity
	C. The speed
	D. Dimensions Option “A” is correct. Pitch of the sound depends upon its frequency. As the pitch of the sound is directly proportional to frequency, Low-frequency sounds are said to have low pitch whereas sounds of high frequency are said to have the high pitch.

60.	Which is used to clean the internal parts of planes
	A. Ultrasonic waves
	B. Oxalic acid
	C. Inaudible
	D. Carbon dioxide Option “A” is correct

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