Class 9 Science Chapter 10 MCQs – Sound Waves: Characteristics and Applications provides 50 important multiple-choice questions with answers for Class 9 Science students. These MCQs cover sound production and propagation, longitudinal waves, frequency, amplitude, wavelength, pitch, loudness, echo, reverberation, ultrasound, SONAR and applications of sound waves.
1. Sound is produced by:
A. Stationary objects
B. Vibrating objects
C. Objects at rest only
D. Light rays
Answer: B. Vibrating objects
2. Sound is a form of:
A. Matter
B. Energy
C. Force
D. Mass
Answer: B. Energy
3. Sound requires a ______ for its propagation.
A. Vacuum
B. Medium
C. Light source
D. Magnetic field
Answer: B. Medium
4. Which of the following can transmit sound?
A. Solids
B. Liquids
C. Gases
D. All of the above
Answer: D. All of the above
5. Sound cannot travel through:
A. Air
B. Water
C. Steel
D. Vacuum
Answer: D. Vacuum
6. Sound waves in air are:
A. Transverse waves
B. Longitudinal waves
C. Electromagnetic waves
D. Surface waves
Answer: B. Longitudinal waves
7. In a longitudinal sound wave, particles of the medium vibrate:
A. Perpendicular to the direction of wave propagation
B. Parallel to the direction of wave propagation
C. In circular paths only
D. Without moving
Answer: B. Parallel to the direction of wave propagation
8. The regions of high pressure and density in a longitudinal sound wave are called:
A. Rarefactions
B. Compressions
C. Crests
D. Troughs
Answer: B. Compressions
9. The regions of low pressure and density in a sound wave are called:
A. Compressions
B. Rarefactions
C. Crests
D. Nodes
Answer: B. Rarefactions
10. The distance between two consecutive compressions is equal to:
A. Amplitude
B. Frequency
C. Wavelength
D. Time period
Answer: C. Wavelength
11. The maximum displacement of a vibrating particle from its mean position is called:
A. Frequency
B. Amplitude
C. Wavelength
D. Time period
Answer: B. Amplitude
12. The SI unit of frequency is:
A. Metre
B. Second
C. Hertz
D. Decibel
Answer: C. Hertz
13. One hertz is equal to:
A. One vibration per second
B. One vibration per minute
C. One metre per second
D. One cycle per minute
Answer: A. One vibration per second
14. The number of vibrations made by an object in one second is called:
A. Amplitude
B. Frequency
C. Time period
D. Wavelength
Answer: B. Frequency
15. The time required to complete one vibration is called:
A. Frequency
B. Wavelength
C. Time period
D. Amplitude
Answer: C. Time period
16. The relationship between frequency and time period is:
A. f = T
B. f = 1/T
C. f = T²
D. f = 2T
Answer: B. f = 1/T
17. If the frequency of a sound wave is 50 Hz, its time period is:
A. 0.02 s
B. 0.2 s
C. 2 s
D. 50 s
Answer: A. 0.02 s
18. If the time period of a vibration is 0.01 s, its frequency is:
A. 10 Hz
B. 50 Hz
C. 100 Hz
D. 1000 Hz
Answer: C. 100 Hz
19. The speed of a wave is given by:
A. v = fλ
B. v = f/λ
C. v = λ/f
D. v = f + λ
Answer: A. v = fλ
20. A sound wave has a frequency of 500 Hz and wavelength of 0.68 m. Its speed is:
A. 34 m/s
B. 340 m/s
C. 680 m/s
D. 250 m/s
Answer: B. 340 m/s
21. If the frequency of a sound wave increases while its speed remains constant, its wavelength:
A. Increases
B. Decreases
C. Remains the same
D. Becomes zero
Answer: B. Decreases
22. The characteristic of sound that enables us to distinguish between a high-pitched and a low-pitched sound is:
A. Loudness
B. Pitch
C. Quality
D. Amplitude
Answer: B. Pitch
23. Pitch of a sound mainly depends on:
A. Frequency
B. Amplitude
C. Speed
D. Wavelength only
Answer: A. Frequency
24. A sound having a higher frequency has:
A. Lower pitch
B. Higher pitch
C. Lower loudness
D. No pitch
Answer: B. Higher pitch
25. Loudness of sound mainly depends on:
A. Frequency
B. Amplitude
C. Wavelength
D. Time period
Answer: B. Amplitude
26. A sound with greater amplitude is generally perceived as:
A. Louder
B. Softer
C. Higher pitched
D. Lower pitched
Answer: A. Louder
27. The characteristic that helps distinguish sounds of the same pitch and loudness produced by different sources is:
A. Frequency
B. Quality or timbre
C. Amplitude
D. Speed
Answer: B. Quality or timbre
28. Which sound has the highest pitch?
A. 100 Hz
B. 250 Hz
C. 500 Hz
D. 1000 Hz
Answer: D. 1000 Hz
29. Which sound is louder if both sounds have the same frequency?
A. The sound with smaller amplitude
B. The sound with greater amplitude
C. Both are always equally loud
D. The sound with lower speed
Answer: B. The sound with greater amplitude
30. The normal human audible frequency range is approximately:
A. 2 Hz to 200 Hz
B. 20 Hz to 20,000 Hz
C. 200 Hz to 2,000 Hz
D. 2,000 Hz to 200,000 Hz
Answer: B. 20 Hz to 20,000 Hz
31. Sounds having frequencies below 20 Hz are called:
A. Ultrasonic sounds
B. Infrasonic sounds
C. Audible sounds
D. Supersonic sounds
Answer: B. Infrasonic sounds
32. Sounds having frequencies above 20,000 Hz are called:
A. Infrasonic sounds
B. Audible sounds
C. Ultrasonic sounds
D. Musical sounds
Answer: C. Ultrasonic sounds
33. Which animal can hear ultrasonic sounds?
A. Dog
B. Human
C. Both A and some other animals
D. Neither
Answer: C. Both A and some other animals
34. Bats use ultrasonic sound mainly for:
A. Photosynthesis
B. Echolocation and navigation
C. Respiration
D. Digestion
Answer: B. Echolocation and navigation
35. SONAR is based mainly on the phenomenon of:
A. Refraction of light
B. Reflection of sound
C. Dispersion of light
D. Absorption of light
Answer: B. Reflection of sound
36. SONAR is commonly used to:
A. Measure the depth of the sea
B. Measure air temperature
C. Produce electricity
D. Measure atmospheric pressure
Answer: A. Measure the depth of the sea
37. The reflection of sound is called:
A. Echo
B. Refraction
C. Dispersion
D. Interference only
Answer: A. Echo
38. For a distinct echo to be heard by a human ear, the reflected sound should generally reach the ear after at least:
A. 0.01 s
B. 0.1 s
C. 1 s
D. 10 s
Answer: B. 0.1 s
39. If the speed of sound is approximately 340 m/s, the minimum distance of a reflecting surface required to hear a distinct echo is approximately:
A. 5 m
B. 10 m
C. 17 m
D. 34 m
Answer: C. 17 m
40. Echoes are commonly heard in:
A. Open fields only
B. Large empty halls and mountainous regions
C. Vacuum chambers
D. Small soundproof rooms only
Answer: B. Large empty halls and mountainous regions
41. The repetition of sound caused by multiple reflections in a large enclosed space is called:
A. Pitch
B. Reverberation
C. Frequency
D. Resonance only
Answer: B. Reverberation
42. Which material is commonly used in auditoriums to reduce unwanted reflections of sound?
A. Hard marble only
B. Sound-absorbing materials
C. Metal sheets only
D. Glass only
Answer: B. Sound-absorbing materials
43. The speed of sound is generally greatest in:
A. Gases
B. Liquids
C. Solids
D. Vacuum
Answer: C. Solids
44. The speed of sound in air generally increases when:
A. Temperature increases
B. Temperature decreases
C. Air disappears
D. Frequency becomes zero
Answer: A. Temperature increases
45. Which statement about sound is correct?
A. Sound can travel through vacuum
B. Sound is an electromagnetic wave
C. Sound needs a material medium for propagation
D. Sound always travels at the speed of light
Answer: C. Sound needs a material medium for propagation
46. A vibrating tuning fork produces sound because it:
A. Produces light
B. Causes vibrations in the surrounding medium
C. Creates a vacuum
D. Produces magnetic waves
Answer: B. Causes vibrations in the surrounding medium
47. When the amplitude of a sound wave is increased, its:
A. Loudness generally increases
B. Pitch always increases
C. Frequency becomes zero
D. Wavelength always becomes zero
Answer: A. Loudness generally increases
48. When the frequency of a sound wave is increased, its:
A. Pitch increases
B. Loudness necessarily increases
C. Amplitude necessarily increases
D. Speed in the same medium necessarily increases
Answer: A. Pitch increases
49. A sound wave travels through air with a speed of 340 m/s and has a frequency of 170 Hz. Its wavelength is:
A. 0.5 m
B. 1 m
C. 2 m
D. 4 m
Answer: C. 2 m
50. Which of the following is an important application of ultrasound?
A. Medical imaging
B. Measuring the depth of oceans using SONAR
C. Detecting internal flaws in materials
D. All of the above
Answer: D. All of the above