NCERT Class 9 Science MCQ
Chapter 10: Sound Waves: Characteristics and Applications
1. Sound is produced by:
(A) stationary objects
(B) vibrating objects
(C) transparent objects
(D) magnetic objects
Answer: (B)
2. The periodic to and fro motion of an object is called:
(A) vibration
(B) reflection
(C) refraction
(D) propagation
Answer: (A)
3. In humans, sound is produced by the vibration of:
(A) eardrum
(B) vocal cords
(C) cochlea
(D) tongue
Answer: (B)
4. A tuning fork is generally made of:
(A) wood
(B) rubber
(C) steel or aluminium
(D) glass
Answer: (C)
5. Sound can propagate through:
(A) solids only
(B) liquids only
(C) gases only
(D) solids, liquids and gases
Answer: (D)
6. The material through which sound propagates is called:
(A) source
(B) medium
(C) vacuum
(D) oscillator
Answer: (B)
7. Sound cannot propagate through:
(A) water
(B) steel
(C) air
(D) vacuum
Answer: (D)
8. The vacuum bell jar experiment shows that sound:
(A) needs a medium to propagate
(B) travels faster in vacuum
(C) is produced only by bells
(D) cannot travel through air
Answer: (A)
9. In outer space, astronauts cannot directly hear each other because:
(A) sound travels too fast
(B) there is no material medium for sound propagation
(C) their spacesuits absorb all sound
(D) sound has no energy
Answer: (B)
10. A sound wave consists of alternating:
(A) crests and troughs only
(B) compressions and rarefactions
(C) nodes and antinodes
(D) peaks and valleys
Answer: (B)
11. A region of higher density in a sound wave is called:
(A) rarefaction
(B) compression
(C) amplitude
(D) wavelength
Answer: (B)
12. A region of lower density in a sound wave is called:
(A) compression
(B) crest
(C) rarefaction
(D) trough
Answer: (C)
13. In a sound wave, particles of the medium:
(A) travel continuously with the wave
(B) remain permanently displaced
(C) vibrate about their mean positions
(D) move only in vacuum
Answer: (C)
14. Sound waves in air are:
(A) transverse mechanical waves
(B) longitudinal mechanical waves
(C) electromagnetic waves
(D) stationary waves only
Answer: (B)
15. In a longitudinal wave, particles vibrate:
(A) perpendicular to wave propagation
(B) parallel to wave propagation
(C) randomly in all directions
(D) only upward
Answer: (B)
16. In a transverse wave, particles vibrate:
(A) parallel to wave propagation
(B) perpendicular to wave propagation
(C) without vibration
(D) only along the wave source
Answer: (B)
17. Which of the following is a mechanical wave?
(A) Light
(B) Sound
(C) Radio wave
(D) X-ray
Answer: (B)
18. Which wave can travel through vacuum?
(A) Sound
(B) Mechanical wave
(C) Light
(D) Sound wave in air
Answer: (C)
19. The energy transferred by a sound wave is carried through the medium by:
(A) permanent movement of particles
(B) vibrations and collisions of particles
(C) movement of the source
(D) movement of vacuum
Answer: (B)
20. The distance between two consecutive compressions is called:
(A) amplitude
(B) frequency
(C) wavelength
(D) time period
Answer: (C)
21. The SI unit of wavelength is:
(A) hertz
(B) second
(C) metre
(D) decibel
Answer: (C)
22. The number of complete oscillations per unit time is called:
(A) amplitude
(B) frequency
(C) wavelength
(D) intensity
Answer: (B)
23. The SI unit of frequency is:
(A) metre
(B) second
(C) hertz
(D) decibel
Answer: (C)
24. The time taken for one complete oscillation is called:
(A) wavelength
(B) frequency
(C) time period
(D) amplitude
Answer: (C)
25. The relation between frequency and time period is:
(A) ν = T
(B) ν = 1/T
(C) ν = T²
(D) ν = 1 + T
Answer: (B)
26. If the frequency of a sound wave is 5 Hz, its time period is:
(A) 5 s
(B) 0.5 s
(C) 0.2 s
(D) 2 s
Answer: (C)
27. If 20 compressions pass a point in 4 seconds, the frequency is:
(A) 80 Hz
(B) 5 Hz
(C) 10 Hz
(D) 0.2 Hz
Answer: (B)
28. A sound wave with a larger amplitude carries:
(A) less energy
(B) more energy
(C) no energy
(D) the same energy in every case
Answer: (B)
29. The amount of sound energy passing through unit area perpendicular to the direction of propagation in unit time is called:
(A) loudness
(B) pitch
(C) intensity
(D) frequency
Answer: (C)
30. As a sound wave travels farther from its source, its intensity generally:
(A) increases
(B) remains constant
(C) decreases
(D) becomes infinite
Answer: (C)
31. The speed of a sound wave is given by:
(A) v = λν
(B) v = λ/ν
(C) v = ν/λ
(D) v = λ + ν
Answer: (A)
32. If wavelength is 2 m and frequency is 100 Hz, the speed of sound is:
(A) 50 m/s
(B) 100 m/s
(C) 200 m/s
(D) 400 m/s
Answer: (C)
33. Sound travels fastest in:
(A) gases
(B) liquids
(C) solids
(D) vacuum
Answer: (C)
34. Sound travels slowest in:
(A) solids
(B) liquids
(C) gases
(D) steel
Answer: (C)
35. According to the chapter, the approximate speed of sound in air at 15 °C is:
(A) 1500 m/s
(B) 5000 m/s
(C) 340 m/s
(D) 3440 m/s
Answer: (C)
36. The speed of sound in water at 15 °C is approximately:
(A) 340 m/s
(B) 1500 m/s
(C) 5000 m/s
(D) 331 m/s
Answer: (B)
37. The speed of sound in steel at 15 °C is approximately:
(A) 340 m/s
(B) 1500 m/s
(C) 5000 m/s
(D) 344 m/s
Answer: (C)
38. The human audible range of sound is approximately:
(A) 2 Hz to 200 Hz
(B) 20 Hz to 20 kHz
(C) 200 Hz to 2000 Hz
(D) 20 kHz to 200 kHz
Answer: (B)
39. Sound waves having frequency below 20 Hz are called:
(A) ultrasonic waves
(B) infrasonic waves
(C) audible waves
(D) sonic waves
Answer: (B)
40. Sound waves having frequency above 20 kHz are called:
(A) infrasonic waves
(B) ultrasonic waves
(C) audible waves
(D) subsonic waves
Answer: (B)
41. Which animal can detect infrasonic waves according to the chapter?
(A) Elephant
(B) Dog
(C) Cat
(D) Bat
Answer: (A)
42. Which group of animals can detect ultrasonic waves?
(A) Dogs, cats, bats and dolphins
(B) Elephants only
(C) Humans only
(D) Plants and insects only
Answer: (A)
43. The perception of frequency by humans is called:
(A) loudness
(B) pitch
(C) intensity
(D) amplitude
Answer: (B)
44. A whistle generally has:
(A) low pitch
(B) high pitch
(C) zero pitch
(D) no frequency
Answer: (B)
45. Human perception of the amplitude of a sound wave is called:
(A) pitch
(B) wavelength
(C) loudness
(D) frequency
Answer: (C)
46. Sound loudness is commonly measured in:
(A) hertz
(B) metre
(C) decibel
(D) second
Answer: (C)
47. The bouncing back of sound waves from a surface is called:
(A) refraction
(B) reflection
(C) absorption
(D) vibration
Answer: (B)
48. An echo can be heard separately when the time gap between the original and reflected sound is at least:
(A) 0.01 s
(B) 0.05 s
(C) 0.1 s
(D) 1 s
Answer: (C)
49. Taking the speed of sound as 340 m/s, the minimum distance of a reflecting surface for hearing an echo is approximately:
(A) 8.5 m
(B) 17 m
(C) 34 m
(D) 68 m
Answer: (B)
50. The ability of bats to locate objects using reflected ultrasonic waves is called:
(A) resonance
(B) reverberation
(C) echolocation
(D) interference
Answer: (C)
NCERT Class 9 Science MCQ Chapter 10: Sound Waves: Characteristics and Applications
ASSERTION–REASON QUESTIONS
Directions: Choose the correct option:
(A) Both A and R are true, and R is the correct explanation of A.
(B) Both A and R are true, but R is not the correct explanation of A.
(C) A is true, but R is false.
(D) A is false, but R is true.
- Assertion (A): Sound cannot propagate through vacuum.
Reason (R): Sound needs a material medium to propagate.
Answer: (A)
- Assertion (A): Sound waves in air are longitudinal waves.
Reason (R): The particles of the medium vibrate parallel to the direction of wave propagation.
Answer: (A)
- Assertion (A): The particles of a medium travel continuously with a sound wave.
Reason (R): The particles of the medium only vibrate about their mean positions.
Answer: (D)
- Assertion (A): A sound wave with greater amplitude carries more energy.
Reason (R): A larger amplitude corresponds to a larger change in the density of the medium.
Answer: (A)
- Assertion (A): Increasing the frequency of a sound wave always increases its speed in the same medium.
Reason (R): In most media, the speed of sound depends on the medium and not on the source or frequency.
Answer: (D)
- Assertion (A): A high-pitched sound has a higher frequency.
Reason (R): Pitch is the way humans perceive the frequency of a sound.
Answer: (A)
- Assertion (A): An echo is produced due to the reflection of sound.
Reason (R): Sound waves can bounce off hard surfaces and return to the listener.
Answer: (A)
- Assertion (A): A reflecting surface must be at least about 17 m away to hear a distinct echo in air when the speed of sound is 340 m/s.
Reason (R): A time gap of at least 0.1 s is required to hear the reflected sound separately.
Answer: (A)
- Assertion (A): Sound waves with frequencies above 20 kHz are called infrasonic waves.
Reason (R): Sound waves with frequencies above 20 kHz are called ultrasonic waves.
Answer: (D)
- Assertion (A): Bats can locate objects in darkness using echolocation.
Reason (R): Bats emit ultrasonic waves and sense the echoes reflected from nearby objects.
Answer: (A)
