Sound Part 2: MCQs (Q26–Q50)
🎵 Sound – Class 9 Science MCQs
Section 2: Characteristics of Sound – Loudness, Pitch, Quality & Speed of Sound (Q26–Q50)
Q26. The loudness of sound depends on:
A. Frequency
B. Amplitude
C. Wavelength
D. Speed
✅ Correct Answer: B. Amplitude
Explanation:
- Loudness ∝ square of amplitude.
Q27. If amplitude of vibration doubles, loudness becomes:
A. 2 times
B. 4 times
C. 8 times
D. Same
✅ Correct Answer: B. 4 times
Q28. The pitch of sound depends on:
A. Frequency
B. Amplitude
C. Wavelength
D. Medium
✅ Correct Answer: A. Frequency
Explanation:
- Higher frequency → higher pitch.
Q29. A high-pitched sound has:
A. Large amplitude
B. High frequency
C. Low frequency
D. Both A and B
✅ Correct Answer: B. High frequency
Q30. The quality of sound is determined by:
A. Amplitude
B. Waveform
C. Frequency
D. Velocity
✅ Correct Answer: B. Waveform
Explanation:
- Waveform gives timbre, helping us distinguish voices/instruments.
Q31. Which physical quantity remains constant when sound travels from one medium to another?
A. Frequency
B. Wavelength
C. Velocity
D. Amplitude
✅ Correct Answer: A. Frequency
Explanation:
- Frequency depends only on source, not medium.
Q32. Speed of sound in air depends mainly on:
A. Pressure
B. Density
C. Temperature
D. Humidity
✅ Correct Answer: C. Temperature
Explanation:
- Higher temperature → faster particle vibration → higher speed.
Q33. Effect of humidity on speed of sound in air is:
A. Decreases speed
B. Increases speed
C. No effect
D. Random
✅ Correct Answer: B. Increases speed
Explanation:
- Water vapour lighter than nitrogen/oxygen → decreases effective density.
Q34. The speed of sound in air at 0°C is:
A. 300 m/s
B. 330 m/s
C. 343 m/s
D. 360 m/s
✅ Correct Answer: B. 330 m/s
Q35. Sound travels fastest in:
A. Air
B. Water
C. Iron
D. Glass
✅ Correct Answer: C. Iron
Explanation:
- Speed: solids > liquids > gases.
Q36. Which factor does NOT affect the speed of sound in a medium?
A. Temperature
B. Density
C. Elasticity
D. Amplitude
✅ Correct Answer: D. Amplitude
Explanation:
- Amplitude changes loudness, not speed.
Q37. Which of the following has least speed of sound?
A. Steel
B. Water
C. Oxygen gas
D. Copper
✅ Correct Answer: C. Oxygen gas
Q38. SI unit of loudness (sound intensity) is:
A. Newton
B. Pascal
C. Decibel (dB)
D. Hertz
✅ Correct Answer: C. Decibel (dB)
Q39. Normal range of audible intensity for human ear is about:
A. 0–10 dB
B. 0–120 dB
C. 20–200 dB
D. 0–2000 dB
✅ Correct Answer: B. 0–120 dB
Q40. Which quantity remains same for all sounds of same pitch?
A. Frequency
B. Loudness
C. Amplitude
D. Quality
✅ Correct Answer: A. Frequency
Q41. The shrillness of sound depends on:
A. Frequency
B. Amplitude
C. Quality
D. Speed
✅ Correct Answer: A. Frequency
Q42. Which parameter helps us distinguish between a man’s and woman’s voice of same loudness?
A. Amplitude
B. Frequency
C. Quality
D. Pitch
✅ Correct Answer: C. Quality
Q43. A sound of 10 Hz frequency is called:
A. Audible
B. Ultrasonic
C. Infrasonic
D. Supersonic
✅ Correct Answer: C. Infrasonic
Q44. A sound of 40,000 Hz is:
A. Audible
B. Infrasonic
C. Ultrasonic
D. Supersonic
✅ Correct Answer: C. Ultrasonic
Q45. Which sound wave property changes when source moves towards observer?
A. Amplitude
B. Frequency (Doppler effect)
C. Quality
D. Loudness
✅ Correct Answer: B. Frequency (Doppler effect)
Q46. Which wave characteristic is related to ‘pitch’?
A. Amplitude
B. Wavelength
C. Frequency
D. Waveform
✅ Correct Answer: C. Frequency
Q47. A person increases volume of radio. Which wave property increases?
A. Frequency
B. Amplitude
C. Wavelength
D. Speed
✅ Correct Answer: B. Amplitude
Q48. Which sound property allows us to identify a friend’s voice on phone?
A. Loudness
B. Pitch
C. Quality (Timbre)
D. Frequency
✅ Correct Answer: C. Quality (Timbre)
Q49. The phenomenon of different people producing different sounds of same pitch and loudness is due to:
A. Frequency
B. Amplitude
C. Waveform (Timbre)
D. Speed
✅ Correct Answer: C. Waveform (Timbre)
Q50. If wavelength of sound in air = 1.65 m and frequency = 200 Hz, speed of sound = ?
A. 200 m/s
B. 300 m/s
C. 330 m/s
D. 400 m/s
✅ Correct Answer: C. 330 m/s
Explanation:
- v = f × λ = 200 × 1.65 = 330 m/s.
Sound Class 9 Science, CBSE Class 9 Science MCQs, NCERT Class 9 sound questions, Class 9 Science exam practice, Online learning Science Class 9, sound class 9 science mcqs with answers, cbse class 9 science sound multiple choice questions, ncert class 9 sound quiz online, important mcqs for cbse class 9 science sound chapter, sound class 9 mcqs for online learning