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41. Sounds of frequencies less than 20Hz is _____ waves.
A. Infrasonic
B. Ultrasonic
C. Audible range
D. None of these
ANSWER:A
SOLUTION :Sound waves with a frequency smaller than 20 Hz are called infrasound. Rhinoceroses communicate using infrasound of frequency as low as 5 Hz.
42. Unpleasant sounds are called ____.
A. Shrill
B. Feeble
C. Noise
D. None of these
ANSWER:C
SOLUTION:Unwanted or unpleasant sounds are known as noise.
43. The loudness of sound depends on _____.
A. Its amplitude
B. Its frequency
C. Its time period
D. Its speed
ANSWER:A
SOLUTION:The loudness of sound depends on its amplitude, which is the distance between the resting position and the highest displacement of a sound wave.
44. Pitch of sound is determined by its ____.
A. Frequency
B. Speed
C. Amplitude
D. Loudness
ANSWER:A
SOLUTION:Frequency determines the pitch of sound. The more the frequency, the more will be the pitch or shrillness of a voice.
45. Equivalent unit of Hertz is ____.
A. m-1
B. s
C. m/s
D. s-1
ANSWER:B
SOLUTION:S-1 is equal to Hertz, which is the unit of frequency. The frequency of a wave is the number of waves that pass a given point per second.
46. When the amplitude of vibration is large, sound produced is _____.
A. No sound
B. Feeble
C. Loud
D. None of these
ANSWER:C
SOLUTION :When the amplitude of vibration is large, the sound produced is louder.
47. Ultrasound equipment works at frequency _____.
A. Higher than 10,000 Hz
B. Higher than 20,000 Hz
C. Lower than 10,000 Hz
D. Lower than 20,000 Hz
ANSWER:B
SOLUTION:Ultrasound equipment works at frequencies higher than 20,000 Hz. Ultrasound is sound with a frequency that is above the range of human hearing, which is 20 Hz to 20,000 Hz. Most ultrasound probes operate at frequencies in the megahertz (MHz) range.
48. Frequency of sound is lowest for ____.
A. Woman
B. Young boy
C. Young girl
D. Man
ANSWER:D
SOLUTION: The frequency of a sound is proportional to its pitch. An adult man’s voice has a lower pitch than the voices of a baby boy, a baby girl, and a woman.
49. The distance between two consecutive crest or trough is called ____.
A. Wavelength
B. Frequency
C. Time period
D. Wave number
ANSWER:A
SOLUTION: The distance between two consecutive crests or troughs of a wave is called its wavelength. Wavelength is the distance over which the wave’s shape repeats, and is usually represented by the Greek letter lambda (λ). The SI unit for wavelength is the meter (m).
50. 1 hertz is equal to _____.
A. 1 Vibration per minute
B. 10 Vibrations per minute
C. 60 Vibrations per minute
D. 600 Vibrations per minute
ANSWER:C
SOLUTION: 1 hertz (Hz) is equal to 60 vibrations per minute. Hertz is the SI unit for frequency, which measures the number of vibrations or oscillations a body completes per second. In one minute, a body that completes one vibration or oscillation per second will complete 60 oscillations.