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31. Which part of the ear is called ‘pinna’?
A. Middle
B. Inner
C. Outer
D. None of these
ANSWER:C
SOLUTION :The outer ear consists of the visible portion on the side of the head, known as the pinna [1], and the external auditory canal (ear canal) [2].
32. What collects the sound from the surroundings?
A. Ear drum
B. Pinna
C. Cochlea
D. None of these
ANSWER:B
SOLUTION:The auricle (pinna) is the visible portion of the outer ear. It collects sound waves and channels them into the ear canal (external auditory meatus), where the sound is amplified.
33. In SONAR, we use _____.
A. Ultrasonic waves
B. Infrasonic waves
C. Radio waves
D. Audible sound waves
ANSWER:A
SOLUTION:SONAR, or Sound Navigation and Ranging, uses ultrasonic waves to detect objects underwater, measure depth, and communicate.
34. When we change feeble sound to loud sound we increase its ____.
A. Frequency
B. Amplitude
C. Velocity
D. Wavelength
ANSWER:B
SOLUTION:When a feeble sound is changed to a loud sound, its amplitude increases. Amplitude is the height of a sound wave, and loudness is directly proportional to amplitude. In fact, loudness is proportional to the square of the amplitude.
35. Earthquake produces which kind of sound before the main shock wave begins _____.
A. Ultrasound
B. Infrasound
C. Audible sound
D. None of these
ANSWER:B
SOLUTION:Earthquakes produce infrasound before the main shock wave begins. Infrasound is a low-frequency sound, with a frequency of less than 20 hertz (Hz) or cycles per second. This is below the normal limit of human hearing, which is 20 Hz to 20,000 Hz.
36. Infrasound can be heard by _____.
A. Dog
B. Bat
C. Rhinoceros
D. Human beings
ANSWER:C
SOLUTION :Infrasound has a frequency of less than 20 Hz and Rhinoceroses communicate using Infrasound waves of the frequency of 5 Hz hence rhinoceros is the right answer.
37. At the end of the auditory canal there is a thin membrane called the _____.
A. Pinna
B. Ear drum
C. Stirrup
D. None of these
ANSWER:B
SOLUTION:The thin membrane at the end of the auditory canal is called the eardrum, or tympanic membrane.
38. In humans, the sound is produced by the voice box which called ____.
A. Larynx
B. Pharynx
C. Ear drum
D. None of these
ANSWER:A
SOLUTION: The voice box in the throat, called the larynx, is responsible for the production of sound.
39. Sound needs a ____ for propagation.
A. Temperature
B. Pressure
C. Medium
D. None of these
ANSWER:C
SOLUTION: Amplitude Modulation (AM) is preferred for picture transmission on TV because of the following reasons: The distortion which arises due to interference between multiple signals is more in FM than AM because the frequency of the FM signal continuously changes.
40. Above _____ dB the noise becomes physically painful.
A. 60
B. 70
C. 80
D. None of these
ANSWER:C
SOLUTION: Above 80dB the sound becomes physically painful.