Sound Part 4: MCQs (Q76–Q100)
🔊 Sound – MCQs for Class 8 Science
Part 4: Q76–Q100
Q76. Which of these is a string instrument?
A) Tabla
B) Veena
C) Flute
D) Trumpet
✅ Correct Answer: B) Veena
Explanation:
- B) ✔ Veena produces sound by vibrating strings.
- A, C, D – Produce sound differently.
Q77. Which of these is a percussion instrument?
A) Guitar
B) Drum
C) Flute
D) Violin
✅ Correct Answer: B) Drum
Explanation:
- B) ✔ Drums produce sound when struck.
Q78. Which organ in humans produces sound?
A) Tongue
B) Larynx (voice box)
C) Nose
D) Eardrum
✅ Correct Answer: B) Larynx (voice box)
Explanation:
- B) ✔ Vocal cords in larynx vibrate → sound.
Q79. The number of compressions or rarefactions passing a point per second is:
A) Amplitude
B) Frequency
C) Loudness
D) Timbre
✅ Correct Answer: B) Frequency
Explanation:
- B) ✔ Frequency = number of wave cycles per second.
Q80. Which of the following is NOT an application of ultrasound?
A) Scanning organs
B) SONAR
C) Cleaning spiral tubes
D) Cooking food
✅ Correct Answer: D) Cooking food
Explanation:
- D) ✔ Ultrasound isn’t used in cooking.
Q81. The sensation of sound persists in our ears for about:
A) 1/10th second
B) 1 second
C) 1 minute
D) 1/100th second
✅ Correct Answer: A) 1/10th second
Explanation:
- A) ✔ Persistence of hearing (after-sound) lasts 0.1 s.
Q82. Sound of a lion’s roar is:
A) Infrasonic
B) Audible
C) Ultrasonic
D) Supersonic
✅ Correct Answer: B) Audible
Explanation:
- B) ✔ Within human hearing range.
Q83. SONAR stands for:
A) Sound Navigation and Ranging
B) Solar Navigation and Recording
C) Sound Noise and Recording
D) Sound Navigation and Reflection
✅ Correct Answer: A) Sound Navigation and Ranging
Explanation:
- A) ✔ Correct full form.
Q84. Which sound property helps us identify a singer’s voice?
A) Loudness
B) Pitch
C) Timbre (quality)
D) Frequency
✅ Correct Answer: C) Timbre (quality)
Explanation:
- C) ✔ Timbre distinguishes voices of same pitch/loudness.
Q85. If amplitude of sound decreases, loudness:
A) Increases
B) Decreases
C) Remains same
D) Becomes infinite
✅ Correct Answer: B) Decreases
Explanation:
- B) ✔ Loudness ∝ amplitude².
Q86. Sound waves in air are:
A) Mechanical and longitudinal
B) Mechanical and transverse
C) Electromagnetic and longitudinal
D) Electromagnetic and transverse
✅ Correct Answer: A) Mechanical and longitudinal
Explanation:
- A) ✔ Sound needs medium and consists of compressions/rarefactions.
Q87. An echo is distinctly heard if the distance between source and reflector is at least:
A) 10 m
B) 17 m
C) 100 m
D) 1 m
✅ Correct Answer: B) 17 m
Explanation:
- B) ✔ Sound must return after 0.1 s → ~17 m distance.
Q88. Which animal uses ultrasound for navigation?
A) Dog
B) Bat
C) Elephant
D) Cow
✅ Correct Answer: B) Bat
Explanation:
- B) ✔ Bats use echolocation with ultrasound.
Q89. The speed of sound in steel is about:
A) 340 m/s
B) 1500 m/s
C) 5000 m/s
D) 300,000 km/s
✅ Correct Answer: C) 5000 m/s
Explanation:
- C) ✔ Much faster in solids than air/water.
Q90. A sound with frequency 25,000 Hz is:
A) Audible
B) Infrasonic
C) Ultrasonic
D) None
✅ Correct Answer: C) Ultrasonic
Explanation:
- C) ✔ >20,000 Hz = ultrasonic.
Q91. Sound waves transfer:
A) Only matter
B) Only energy
C) Matter and energy both
D) Neither
✅ Correct Answer: B) Only energy
Explanation:
- B) ✔ Particles oscillate but don’t move permanently.
Q92. Which of the following instruments uses the reflection of sound?
A) Microscope
B) Sonar
C) Telescope
D) Thermometer
✅ Correct Answer: B) Sonar
Explanation:
- B) ✔ SONAR works on reflection of sound.
Q93. Which wave property decides whether sound is soft or loud?
A) Frequency
B) Amplitude
C) Pitch
D) Quality
✅ Correct Answer: B) Amplitude
Explanation:
- B) ✔ Greater amplitude → louder sound.
Q94. Which phenomenon makes sound heard around a corner?
A) Reflection
B) Refraction
C) Diffraction
D) Polarisation
✅ Correct Answer: C) Diffraction
Explanation:
- C) ✔ Sound bends around obstacles due to diffraction.
Q95. Which sound wave property is measured in hertz?
A) Amplitude
B) Frequency
C) Loudness
D) Speed
✅ Correct Answer: B) Frequency
Explanation:
- B) ✔ 1 Hz = 1 oscillation per second.
Q96. Which part of ear maintains balance of the body?
A) Cochlea
B) Semicircular canals
C) Eardrum
D) Pinna
✅ Correct Answer: B) Semicircular canals
Explanation:
- B) ✔ They help in balance, not in hearing sound.
Q97. What is the speed of sound in water?
A) 150 m/s
B) 340 m/s
C) 1500 m/s
D) 5000 m/s
✅ Correct Answer: C) 1500 m/s
Explanation:
- C) ✔ Faster than air, slower than steel.
Q98. Sound intensity is measured in:
A) Newton
B) Joule
C) Watt per square metre
D) Decibel
✅ Correct Answer: C) Watt per square metre
Explanation:
- C) ✔ Intensity = power per unit area.
Q99. If sound takes 3 seconds to travel to a wall and back, distance of wall is (speed = 340 m/s):
A) 340 m
B) 510 m
C) 680 m
D) 170 m
✅ Correct Answer: B) 510 m
Explanation:
- Distance covered = v × t = 340 × 3 = 1020 m (round trip).
- Distance of wall = 1020 ÷ 2 = 510 m.
Q100. Which property of sound helps in identifying different musical instruments?
A) Frequency
B) Loudness
C) Quality (timbre)
D) Amplitude
✅ Correct Answer: C) Quality (timbre)
Explanation:
- C) ✔ Timbre makes sound of flute different from guitar at same pitch/loudness.
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