Class 9 Science Exploration Chapter 10 MCQs – Sound Waves: Characteristics and Applications – practice helps you understand sound waves and applications in a simple, step-by-step way. The chapter shows how vibrating objects produce sound and why sound needs a medium to travel, using the vacuum bell jar experiment. It explains compressions, rarefactions and longitudinal waves, and introduces wavelength, frequency, time period, amplitude and the speed of sound. You will also learn about pitch, loudness, echo, reverberation, infrasonic and ultrasonic waves, echolocation and sonar. These MCQs with answers are based on the new NCERT Exploration textbook and include both concept-based and numerical questions.
Class 9 Science Exploration Chapter 10 MCQs with Answers
Class 9 Science Chapter 10 MCQs Set 1
Q1. What produces sound in a plucked rubber band?
[A]. Its colour
[B]. Its vibration
[C]. Its mass alone
[D]. Its position alone
Q2. Which parts vibrate to produce the human voice?
[A]. Teeth
[B]. Eardrums
[C]. Vocal cords
[D]. Lips only
Q3. What does the bell-jar experiment demonstrate?
[A]. Sound needs a material medium
[B]. The bell stops vibrating when air is removed
[C]. Sound travels best in a vacuum
[D]. Sound cannot travel through air
Q4. Through which of these can sound not propagate?
[A]. Water
[B]. Steel
[C]. A vacuum
[D]. Air
Q5. In a sound wave in air, how do the particles move?
[A]. Only upwards without returning
[B]. Back and forth about their mean positions
[C]. In a permanent flow towards the source
[D]. Continuously from the source to the listener
Class 9 Science Chapter 10 MCQs Set 2
Q6. What is a compression in a sound wave?
[A]. A place where sound stops
[B]. A region with no particles
[C]. A region of below-average density
[D]. A region of above-average density
Q7. What is a rarefaction in a sound wave?
[A]. A region of below-average density
[B]. A region containing no energy
[C]. A region of maximum density
[D]. A region in which all particles stop moving
Q8. Why is sound in air called a longitudinal wave?
[A]. Its particles vibrate parallel to propagation
[B]. It can travel through a vacuum
[C]. Its particles move perpendicular to propagation
[D]. It has no wavelength
Q9. What travels from a tuning fork to a listener through the sound wave?
[A]. The same air particles over the full distance
[B]. A continuous jet of air
[C]. Energy
[D]. The fork’s metal particles
Q10. What is the wavelength of a sound wave?
[A]. Maximum change in density
[B]. Number of vibrations each second
[C]. Distance between successive compressions
[D]. Time between two vibrations
Class 9 Science Chapter 10 MCQs Set 3
Q12. Ten complete oscillations occur in 2 s. What is the frequency?
[A]. 2 Hz
[B]. 5 Hz
[C]. 0.2 Hz
[D]. 20 Hz
Q13. What is the time period of a wave with frequency 5 Hz?
[A]. 2 s
[B]. 10 s
[C]. 5 s
[D]. 0.2 s
Q14. A source vibrates at 20 Hz. How many complete oscillations occur in one minute?
[A]. 60
[B]. 20
[C]. 600
[D]. 1200
Q15. On a density–distance graph, what represents the sound wave’s density amplitude?
[A]. The distance between two crests
[B]. The wave’s total travel distance
[C]. The time for one vibration
[D]. The maximum density change from the average value
Class 9 Science Chapter 10 MCQs Set 4
Q16. For otherwise comparable sound waves in the same medium, a larger amplitude indicates what?
[A]. No energy carried
[B]. More energy carried
[C]. A compulsory increase in frequency
[D]. Less energy carried
Q17. Why does sound intensity generally decrease as one moves farther from a small source in open surroundings?
[A]. The source loses all its mass
[B]. The source loses all its mass
[C]. Its energy spreads over a larger area
[D]. The sound becomes light
Q18. Which equation relates sound speed v, wavelength λ and frequency ν?
[A]. v = λ + ν
[B]. v = ν/λ
[C]. v = λ/ν
[D]. v = λν
Q19. A sound wave travels at 340 m/s and has frequency 170 Hz. What is its wavelength?
[A]. 2 m
[B]. 0.5 m
[C]. 170 m
[D]. 510 m
Q20. A source’s frequency doubles while sound speed in the same air remains constant. What happens to wavelength?
[A]. It doubles
[B]. It stays unchanged
[C]. It becomes four times as large
[D]. It halves
Class 9 Science Chapter 10 MCQs Set 5
Q21. Using the approximate speeds steel = 5000 m/s, water = 1500 m/s and air = 340 m/s, where does sound travel fastest?
[A]. All three equally
[B]. Water
[C]. Steel
[D]. Air
Q22. Lightning is seen 5 s before thunder is heard. If sound travels at 340 m/s and light travel time is neglected, how far away is the lightning?
[A]. 1700 m
[B]. 68 m
[C]. 340 m
[D]. 3400 m
Q23. Which physical property is most closely related to perceived pitch?
[A]. Frequency
[B]. Speed alone
[C]. Source mass alone
[D]. Travel distance alone
Q24. What is the approximate human audible frequency range?
[A]. 0–20 Hz
[B]. 2000–200000 Hz
[C]. 20–20000 Hz
[D]. 20–200 Hz
Class 9 Science Chapter 10 MCQs Set 6
Q26. What allows two instruments playing the same note at the same loudness to sound different?
[A]. Only distance to the listener
[B]. Only wave speed in air
[C]. Timbre
[D]. The absence of vibration
Q27. What causes an echo?
[A]. A change of sound into light
[B]. Reflection of sound from a sufficiently distant surface
[C]. Absorption of every sound wave
[D]. The source vibrating without a medium
Q28. An echo returns after 0.5 s. If sound travels at 340 m/s, how far away is the reflecting wall?
[A]. 680 m
[B]. 85 m
[C]. 170 m
[D]. 340 m
Q29. Why are curtains and sound-absorbing panels used in auditoriums?
[A]. To make sound travel through a vacuum
[B]. To increase every reflection
[C]. To change all sounds into ultrasound
[D]. To reduce excessive reverberation
Q30. A sonar pulse returns from an underwater object after 0.90 s. If sound speed is 1530 m/s, what is the object’s distance?
[A]. 688.5 m
[B]. 1700 m
[C]. 1377 m
[D]. 344.25 m
Chapter 10 Sound Waves at a Glance: 10 Points to Revise
- Sound is produced by vibrating objects, such as a plucked rubber band, a struck tuning fork or our vocal cords. When the vibration stops, the sound stops too.
- Sound needs a medium (solid, liquid or gas) to travel. It cannot travel through a vacuum, so astronauts in space use radio devices to talk to each other.
- A sound wave is a series of compressions (regions of higher density) and rarefactions (regions of lower density). The particles of the medium only vibrate about their mean positions; they do not travel with the wave.
- Sound is a longitudinal and mechanical wave because the particles vibrate parallel to the direction in which the wave travels and the wave needs a medium.
- Wavelength (λ) is the distance between two consecutive crests or troughs. Frequency (ν) is the number of oscillations per second, measured in hertz (Hz). Time period is T = 1/ν.
- The speed of sound is v = λ × ν. Sound travels fastest in solids (steel about 5000 m s⁻¹), slower in liquids (water about 1500 m s⁻¹) and slowest in gases (air about 340 m s⁻¹).
- Pitch depends on frequency, and loudness depends on amplitude. A larger amplitude means more energy and intensity decreases as sound spreads out from the source.
- Humans can hear 20 Hz to 20 kHz. Sound below 20 Hz is infrasonic, which elephants can detect and sound above 20 kHz is ultrasonic, which bats, dogs and dolphins can detect.
- An echo is heard only when the reflected sound arrives at least 0.1 s later, so the reflecting surface must be at least 17 m away. Reverberation happens when many reflections arrive less than 0.05 s apart.
- Ultrasound is used in ultrasonography, breaking kidney stones, cleaning machine parts and finding cracks in metal. Bats use echolocation and ships use sonar to find depth and underwater objects.
Simple Tips to Solve Sound Wave Numericals and MCQs
- For echo and sonar questions, remember that sound goes to the object and comes back, so divide the total distance by 2: distance = (v × t) ÷ 2.
- Convert kHz to Hz (1 kHz = 1000 Hz) and cm to m before using v = λ × ν.
- In a given medium, a higher frequency means a shorter wavelength, because the speed stays the same.
- What travels with a sound wave is energy, not the air particles.
- Do not mix up the terms. Frequency and amplitude can be measured, while pitch and loudness are how we hear them.
Sound is all around us, which makes this one of the most interesting chapters in Class 9 Science. These Class 9 Science Exploration Chapter 10 MCQs connect classroom ideas to everyday experiences: hearing thunder after seeing lightning, the echo in an empty corridor, the whispering gallery of Gol Gumbaz, a car’s parking sensor and a bat hunting in the dark. When you attempt the numerical questions, write the formula first and check the units. Revisit the density-distance graphs, because many questions ask you to read the wavelength and amplitude from them.
Practise Chapter 10 with NCERT Solutions
After this quiz, check our NCERT Solutions for Class 9 Science Exploration Chapter 10 for easy-to-follow answers to all textbook questions. They explain graph-based problems on wavelength and frequency, echo and sonar distance calculations, the parking sensor and thunder delay questions and the air-versus-water cliff problem. Practising both MCQs and solutions will help you understand “Sound Waves: Characteristics and Applications” clearly and score well in your exams.
