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CBSE Class 9  >  Class 9 Test  >  Science New NCERT 2026-27 (New Syllabus)  >  Test: Sound Waves: Characteristics and Applications - 2 - Class 9 MCQ

Sound Waves: Characteristics and Applications - 2 - Free MCQ Practice Test


MCQ Practice Test & Solutions: Test: Sound Waves: Characteristics and Applications - 2 (15 Questions)

You can prepare effectively for Class 9 Science Class 9 New NCERT 2026-27 (New Syllabus) with this dedicated MCQ Practice Test (available with solutions) on the important topic of "Test: Sound Waves: Characteristics and Applications - 2". These 15 questions have been designed by the experts with the latest curriculum of Class 9 2026, to help you master the concept.

Test Highlights:

  • - Format: Multiple Choice Questions (MCQ)
  • - Duration: 15 minutes
  • - Number of Questions: 15

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Test: Sound Waves: Characteristics and Applications - 2 - Question 1
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Which of the following animals uses infrasound for communication?

Detailed Solution: Question 1

Elephants can produce and detect infrasound — sound below 20 Hz. They use infrasonic waves to communicate over very long distances, sometimes several kilometres. Bats and dolphins use ultrasound for echolocation. Dogs and cats can detect ultrasound but are not known for producing infrasound. Infrasound also occurs naturally during earthquakes and volcanic eruptions and travels very long distances.

Test: Sound Waves: Characteristics and Applications - 2 - Question 2
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The number of complete density oscillations at a fixed point per unit time is known as:

Detailed Solution: Question 2

Frequency (ν) is defined as the number of density oscillations at a fixed point per unit time. It represents how often the density at a given position changes from maximum to minimum and back to maximum, completing one full cycle. Its SI unit is hertz (Hz) or per second (s⁻¹). Time period is the time taken for one complete oscillation, wavelength is the distance between two consecutive crests or troughs, and amplitude is the maximum change in density compared to average density.

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Test: Sound Waves: Characteristics and Applications - 2 - Question 3
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If there are 20 density oscillations in 4 seconds at a given position, what is the frequency of the sound wave?

Detailed Solution: Question 3

Frequency = Number of oscillations divided by time taken = 20 divided by 4 = 5 Hz. The time period would be T = 1/ν = 1/5 = 0.2 s. This means the density at that fixed point completes one full oscillation every 0.2 seconds, and this happens 5 times every second.

Test: Sound Waves: Characteristics and Applications - 2 - Question 4
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What is the wavelength of sound for a frequency of 20 Hz if the speed of sound in air is 344 m/s?

Detailed Solution: Question 4

Using v = λ × ν, we get λ = v/ν = 344/20 = 17.2 m. This is the wavelength corresponding to the lowest frequency humans can hear. For the highest audible frequency of 20,000 Hz, λ = 344/20000 = 0.0172 m = 1.72 cm. This shows that wavelengths of audible sound range from about 1.72 cm to 17.2 m — a very wide range.

Test: Sound Waves: Characteristics and Applications - 2 - Question 5
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You clap in an empty corridor and hear an echo after 0.5 s. If speed of sound = 340 m/s, your distance from the wall is:

Detailed Solution: Question 5

Since sound travels to the wall and returns, the total distance covered = speed × time = 340 × 0.5 = 170 m. Distance from wall = 170/2 = 85 m. For an echo to be heard distinctly, the wall must be at least 17 m away so that the reflected sound reaches after at least 0.1 s. Since 85 m is greater than 17 m, a clear echo is heard in this case.

Test: Sound Waves: Characteristics and Applications - 2 - Question 6
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Which of the following best describes the propagation of sound?

Detailed Solution: Question 6

In sound wave propagation, it is the energy which is the density disturbance that travels, not the particles of the medium. Medium particles only oscillate back and forth about their mean positions — they do not travel with the wave. This is analogous to a mark on a slinky: the mark only oscillates back and forth; it does not travel with the disturbance. The compressions and rarefactions move through the medium, transferring energy from particle to particle through collisions.

Test: Sound Waves: Characteristics and Applications - 2 - Question 7
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Prolonged exposure to very loud sound can cause:

Detailed Solution: Question 7

Unwanted or harmful sound is called noise. Prolonged exposure to loud sound above about 85 dB can cause permanent hearing loss, which is tested via audiograms. This is called noise pollution. Sounds from firecrackers can exceed 100 dB and are particularly damaging to hearing. Hearing aids — consisting of a microphone, amplifier, and speaker — are used by people with hearing impairment. Avoiding prolonged exposure to loud noise is the best preventive measure.

Test: Sound Waves: Characteristics and Applications - 2 - Question 8
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The ability to locate objects using reflected sound waves is called:

Detailed Solution: Question 8

Echolocation is the ability to locate objects using reflected sound waves. Bats emit short bursts of ultrasonic waves and by sensing the echoes, they can determine the position of obstacles and prey without using vision. Besides bats, dolphins, whales, and some birds also use echolocation for navigation and hunting. Humans have adapted this principle in SONAR for underwater exploration and in ultrasonography for medical imaging.

Test: Sound Waves: Characteristics and Applications - 2 - Question 9
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The quality of sound that distinguishes two instruments playing the same note at the same loudness is called:

Detailed Solution: Question 9

Timbre is the characteristic that makes two instruments sound different even when they play the same note at the same loudness. It is determined by the shape, material, and construction of the instrument, and the pattern and intensity of overtones produced. A musical note is a combination of a fundamental frequency and overtones, creating a rich sound. A tone from a tuning fork is a single-frequency sound and sounds simpler than a musical note.

Test: Sound Waves: Characteristics and Applications - 2 - Question 10
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Two notes are said to be an octave apart when one note has _______ the frequency of the other.

Detailed Solution: Question 10

An octave is the interval between two notes where one has exactly double the frequency of the other. For example, a note at 200 Hz and a note at 400 Hz are one octave apart. Similarly, 440 Hz and 880 Hz are one octave apart. The higher note always has double the frequency of the lower note. This relationship is fundamental to music theory and applies universally across all musical traditions.

Test: Sound Waves: Characteristics and Applications - 2 - Question 11
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Which of the following is NOT an application of ultrasonic waves?

Detailed Solution: Question 11

Detecting earthquakes and volcanic eruptions is an application of infrasonic waves which are below 20 Hz, not ultrasonic waves. Infrasound travels long distances through air and the Earth, making it useful for detecting geological events. Ultrasonic waves which are above 20 kHz are used for ultrasonography, breaking kidney stones, ultrasonic welding and cleaning, detecting internal defects in metals, and in SONAR for underwater detection.

Test: Sound Waves: Characteristics and Applications - 2 - Question 12
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As sound travels farther from its source, its intensity:

Detailed Solution: Question 12

Intensity is defined as the amount of sound energy passing through a unit area perpendicular to the direction of propagation per unit time. As a sound wave travels away from its source, it spreads out over a larger and larger area in the form of spherical waves. Since the total energy is conserved but spreads over a greater area, the intensity decreases with distance from the source. Sounds with larger initial amplitude carry more energy and can travel farther before intensity reduces to negligible levels.

Test: Sound Waves: Characteristics and Applications - 2 - Question 13
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Which part of the ear first vibrates when sound enters it?

Detailed Solution: Question 13

When sound enters the ear, it first makes the eardrum which is a thin membrane vibrate. Small bones called ossicles in the middle ear then amplify these vibrations. The cochlea in the inner ear converts these amplified vibrations into electrical signals that travel via the auditory nerve to the brain, which interprets them as sound. Having two ears helps the brain determine the direction of sound by comparing which ear receives the sound first — the time difference can be less than a thousandth of a second.

Test: Sound Waves: Characteristics and Applications - 2 - Question 14
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A grasshopper produces sound by:

Detailed Solution: Question 14

Some animals produce sound by striking or rubbing certain body parts together. Grasshoppers and crickets rub their wings or legs to produce their characteristic sounds. This is different from how humans produce sound through vibrating vocal cords, or how a flute produces sound through a vibrating air column inside a hollow pipe. In most biological sound-producing systems, more than one vibrating part is involved.

Test: Sound Waves: Characteristics and Applications - 2 - Question 15
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The speed of sound in a medium depends on which of the following factors?

Detailed Solution: Question 15

The speed of sound depends on the nature of the medium — it is fastest in solids, slower in liquids, and slowest in gases. It also depends on the temperature of the medium — speed increases as temperature increases, from about 331 m/s at 0°C to 344 m/s at 22°C in air. Humidity also affects speed — it increases with humidity. The speed of sound does NOT depend on the frequency, amplitude, or wavelength of the sound. Changing these properties does not change how fast sound travels through a given medium under given conditions.

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About this Class 9 Practice Test

This test contains 15 MCQs on Sound Waves: Characteristics and Applications - 2 with detailed solutions for each question. It is part of the Science Class 9 New NCERT 2026-27 (New Syllabus) course on EduRev, designed to align with the current Class 9 syllabus. Each solution explains not just the correct answer but also gives you an understanding of the topic — not just to attempt the question but also help you prepare for the exam with practice.

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