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CBSE Class 9  >  Class 9 Test  >  Science New NCERT 2026-27 (New Syllabus)  >  Test: Sound Waves: Characteristics and Applications - 1 - Class 9 MCQ

Sound Waves: Characteristics and Applications - 1 - Free MCQ Practice Test


MCQ Practice Test & Solutions: Test: Sound Waves: Characteristics and Applications - 1 (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 - 1". 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 - 1 - Question 1
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What is the primary cause of sound production?

Detailed Solution: Question 1

Sound is produced by vibrations — the periodic to and fro motion of an object. For example, when a stretched rubber band is plucked across a cardboard box, it produces sound as long as it vibrates. When the vibration stops, the sound also stops. The object that produces sound is called the source of sound.

Test: Sound Waves: Characteristics and Applications - 1 - Question 2
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Sound cannot travel through which of the following?

Detailed Solution: Question 2

Sound requires a material medium (solid, liquid, or gas) to propagate. Vacuum is a space where there is no medium at all. This is proven by the vacuum bell jar experiment — when an electric bell is placed inside a bell jar and air is pumped out, the sound becomes fainter and nearly disappears even though the bell is still visibly ringing. When air is let back in, sound is heard again.

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Test: Sound Waves: Characteristics and Applications - 1 - Question 3
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In a sound wave, regions of lower density are called:

Detailed Solution: Question 3

When the piston in a tube moves backward, the air near it becomes less dense — this low-density region is called rarefaction. The high-density region formed when the piston moves forward is called compression. As the piston oscillates, compressions and rarefactions are produced alternately and travel away from the source as a sound wave.

Test: Sound Waves: Characteristics and Applications - 1 - Question 4
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Sound waves are classified as longitudinal mechanical waves because:

Detailed Solution: Question 4

In sound waves, particles of the medium vibrate back and forth parallel to the direction of propagation of the disturbance. Such waves are called longitudinal waves. They are also called mechanical waves because they require a material medium for propagation and cannot travel through vacuum. This is different from transverse waves like light where particles vibrate perpendicular to the direction of propagation.

Test: Sound Waves: Characteristics and Applications - 1 - Question 5
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If the frequency of a sound wave is 50 Hz, what is its time period?

Detailed Solution: Question 5

The relationship between frequency and time period is ν = 1/T, which gives T = 1/ν. Here ν = 50 Hz. Therefore T = 1/50 = 0.02 s. Frequency and time period are inversely related — a shorter time period corresponds to a higher frequency. The SI unit of time period is second and that of frequency is hertz.

Test: Sound Waves: Characteristics and Applications - 1 - Question 6
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The speed of sound in steel is approximately:

Detailed Solution: Question 6

Sound travels at different speeds in different media. At 15°C, the approximate speeds are — Steel: 5000 m/s, Water: 1500 m/s, Air: 340 m/s. Sound travels fastest in solids, slower in liquids, and slowest in gases. Sound travels about 15 to 20 times faster in solids than in air, and about 4 to 5 times faster in water than in air.

Test: Sound Waves: Characteristics and Applications - 1 - Question 7
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A device that converts sound energy into electrical energy is:

Detailed Solution: Question 7

A microphone converts sound energy to electrical energy. Sound waves make a thin membrane called the diaphragm vibrate, and these vibrations are converted into an electrical signal. A speaker does the opposite — it converts electrical energy back to sound energy by making a cone or diaphragm vibrate. An amplifier increases the strength of an electrical signal, and a tuning fork is a device used to produce sound of a specific frequency.

Test: Sound Waves: Characteristics and Applications - 1 - Question 8
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On a density vs distance graph of a sound wave, compressions appear as:

Detailed Solution: Question 8

On a graph that plots density on the y-axis and distance on the x-axis, compressions which are regions of higher density appear as crests which are the highest points on the graph. Rarefactions which are regions of lower density appear as troughs which are the lowest points. A horizontal dashed line marks the average density of the medium.

Test: Sound Waves: Characteristics and Applications - 1 - Question 9
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Human beings can hear sound in the frequency range of:

Detailed Solution: Question 9

The human audible range is 20 Hz to 20,000 Hz (20 kHz). Sound below 20 Hz is called infrasound and above 20,000 Hz is called ultrasound — both are inaudible to humans. This audible range varies from person to person and generally decreases with age. Dogs, cats, bats, and dolphins can hear ultrasound while elephants can detect infrasound.

Test: Sound Waves: Characteristics and Applications - 1 - Question 10
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Lightning is seen 5 seconds before thunder is heard. If the speed of sound is 340 m/s, the distance of the lightning strike is:

Detailed Solution: Question 10

Since light travels almost instantaneously compared to sound, the entire 5-second delay is due to sound travel alone. Distance = speed × time = 340 × 5 = 1700 m which is approximately 1.7 km. This is why we always see lightning before we hear thunder — the difference in speed between light (3 × 10⁸ m/s) and sound (340 m/s) is enormous.

Test: Sound Waves: Characteristics and Applications - 1 - Question 11
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Which of the following is the correct relationship between speed (v), wavelength (λ), and frequency (ν)?

Detailed Solution: Question 11

The speed of sound is defined as the distance a crest or trough travels in unit time. The distance between two consecutive crests equals one wavelength (λ), and this distance is covered in one time period (T). So v = λ/T. Since ν = 1/T, substituting gives v = λ × ν. This formula shows that for a given medium, if wavelength increases, frequency decreases proportionally, keeping speed constant.

Test: Sound Waves: Characteristics and Applications - 1 - Question 12
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What is the minimum distance from a wall required to hear a distinct echo? (Speed of sound = 340 m/s)

Detailed Solution: Question 12

The human brain needs a time gap of at least 0.1 s between the original sound and the reflected sound to perceive them as separate sounds. In 0.1 s, sound covers 340 × 0.1 = 34 m total. Since sound travels to the wall and back, the minimum distance to the wall = 34/2 = 17 m. If the wall is closer than 17 m, the reflected sound merges with the original and we hear reverberation instead of a clear echo.

Test: Sound Waves: Characteristics and Applications - 1 - Question 13
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Reverberation in an auditorium is reduced by using:

Detailed Solution: Question 13

Reverberation occurs when sound undergoes multiple reflections from walls and the reflected sounds arrive with a time difference of less than 0.05 s, causing the sound to persist and become garbled. Soft porous materials like curtains, upholstered chairs, and sound-absorbing panels absorb sound energy rather than reflecting it. Hard smooth surfaces like stone, metal, and glass reflect sound well and increase reverberation. Modern auditoriums are architecturally designed to achieve desirable reverberation levels.

Test: Sound Waves: Characteristics and Applications - 1 - Question 14
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Sound waves with frequency above 20,000 Hz are called:

Detailed Solution: Question 14

Sound waves with frequency above 20,000 Hz (20 kHz) are called ultrasonic waves or ultrasound. They are beyond the upper limit of human hearing. Animals like bats, dolphins, dogs, and cats can detect ultrasound. Ultrasound has many practical applications such as ultrasonography for medical imaging, breaking kidney stones, ultrasonic welding, cleaning delicate machine parts, and detecting defects in metal blocks used in construction.

Test: Sound Waves: Characteristics and Applications - 1 - Question 15
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A naval sonar signal returns after 0.90 s. Speed of sound in seawater = 1530 m/s. How far is the underwater object?

Detailed Solution: Question 15

Since the signal travels to the object and back, the time taken to reach the object = 0.90/2 = 0.45 s. Distance = speed × time = 1530 × 0.45 = 688.5 m. SONAR stands for Sound Navigation and Ranging. It uses ultrasonic waves sent into water and the reflected waves are analysed to determine the distance, direction, and speed of underwater objects such as submarines or shipwrecks.

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About this Class 9 Practice Test

This test contains 15 MCQs on Sound Waves: Characteristics and Applications - 1 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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