Sound Part 1: MCQs (Q1–Q25)
🔊 Sound – MCQs for Class 8 Science
Part 1: Q1–Q25
Q1. Sound is produced due to:
A) Vibrations of objects
B) Reflections of light
C) Heat energy
D) Chemical reaction
✅ Correct Answer: A) Vibrations of objects
Explanation:
- A) ✔ Vibrations of particles create sound waves.
- B) Light reflection relates to vision, not sound.
- C) Heat does not directly produce sound.
- D) Chemical reactions may release energy but not sound necessarily.
Q2. Medium is necessary for propagation of sound because:
A) Sound is electromagnetic
B) Sound is mechanical wave
C) Sound is chemical wave
D) Sound is a form of heat
✅ Correct Answer: B) Sound is mechanical wave
Explanation:
- A) EM waves need no medium.
- B) ✔ Sound is mechanical → needs medium (solid, liquid, gas).
- C, D) Incorrect.
Q3. Which of the following can transmit sound?
A) Vacuum
B) Solids
C) Liquids
D) Gases
✅ Correct Answer: B), C), D) (All mediums except vacuum)
Explanation:
- Vacuum cannot transmit sound.
- Solids, liquids, gases ✔ transmit sound waves.
Q4. The SI unit of frequency is:
A) Hertz
B) Newton
C) Pascal
D) Joule
✅ Correct Answer: A) Hertz
Explanation:
- A) ✔ Hertz = cycles per second.
- B) Newton = force.
- C) Pascal = pressure.
- D) Joule = energy.
Q5. Sound travels fastest in:
A) Air
B) Water
C) Vacuum
D) Steel
✅ Correct Answer: D) Steel
Explanation:
- A) Slowest in gases.
- B) Faster in liquids.
- C) Cannot travel in vacuum.
- D) ✔ Maximum in solids (steel).
Q6. The loudness of sound depends on:
A) Frequency
B) Amplitude
C) Wavelength
D) Speed
✅ Correct Answer: B) Amplitude
Explanation:
- B) ✔ Greater amplitude → louder sound.
- A) Frequency affects pitch.
- C, D) Not directly related.
Q7. Pitch of sound depends on:
A) Amplitude
B) Frequency
C) Speed
D) Wavelength
✅ Correct Answer: B) Frequency
Explanation:
- B) ✔ Higher frequency → higher pitch.
Q8. Which sound can humans hear?
A) <20 Hz
B) 20–20,000 Hz
C) >20,000 Hz
D) All of these
✅ Correct Answer: B) 20–20,000 Hz
Explanation:
- B) ✔ Audible range for humans.
- A) <20 Hz = infrasonic.
- C) >20,000 Hz = ultrasonic.
Q9. Sound waves in air are:
A) Transverse waves
B) Longitudinal waves
C) Electromagnetic waves
D) Surface waves
✅ Correct Answer: B) Longitudinal waves
Explanation:
- B) ✔ Sound consists of compressions and rarefactions → longitudinal.
Q10. The device used to hear sound under water is:
A) Telescope
B) Microscope
C) Stethoscope
D) Hydrophone
✅ Correct Answer: D) Hydrophone
Explanation:
- D) ✔ Hydrophone detects underwater sound.
Q11. Sound cannot travel through:
A) Solids
B) Liquids
C) Gases
D) Vacuum
✅ Correct Answer: D) Vacuum
Explanation:
- D) ✔ No medium in vacuum → no sound transmission.
Q12. The speed of sound in air at room temperature is about:
A) 150 m/s
B) 340 m/s
C) 1000 m/s
D) 1500 m/s
✅ Correct Answer: B) 340 m/s
Explanation:
- B) ✔ Standard value at 25°C.
Q13. The time taken by sound to make one oscillation is called:
A) Amplitude
B) Frequency
C) Period
D) Wavelength
✅ Correct Answer: C) Period
Explanation:
- C) ✔ Time period = reciprocal of frequency.
Q14. What is the range of infrasonic sound?
A) >20,000 Hz
B) 20–20,000 Hz
C) <20 Hz
D) 200–2000 Hz
✅ Correct Answer: C) <20 Hz
Explanation:
- C) ✔ Infrasonic = below 20 Hz.
Q15. The sound above 20,000 Hz is called:
A) Audible
B) Ultrasonic
C) Infrasonic
D) Subsonic
✅ Correct Answer: B) Ultrasonic
Explanation:
- B) ✔ Beyond human hearing = ultrasonic.
Q16. Which animal can hear ultrasonic sounds?
A) Dog
B) Elephant
C) Bat
D) Whale
✅ Correct Answer: C) Bat
Explanation:
- C) ✔ Bats use ultrasound for echolocation.
Q17. The speed of sound depends on:
A) Frequency
B) Amplitude
C) Medium
D) Loudness
✅ Correct Answer: C) Medium
Explanation:
- C) ✔ Sound speed depends on medium’s density and elasticity.
Q18. Sound travels slowest in:
A) Air
B) Water
C) Steel
D) Wood
✅ Correct Answer: A) Air
Explanation:
- A) ✔ Gases have least density → slowest speed.
Q19. Sound cannot travel in space because:
A) It is too cold
B) No medium is present
C) Too hot in space
D) Gravity is weak
✅ Correct Answer: B) No medium is present
Explanation:
- B) ✔ Sound = mechanical wave, requires medium.
Q20. Which property determines shrillness of sound?
A) Amplitude
B) Frequency
C) Loudness
D) Velocity
✅ Correct Answer: B) Frequency
Explanation:
- B) ✔ Higher frequency = more shrill.
Q21. Which wave property is common to both light and sound?
A) Both can travel in vacuum
B) Both show reflection
C) Both are longitudinal
D) Both are transverse
✅ Correct Answer: B) Both show reflection
Explanation:
- B) ✔ Reflection occurs in both.
Q22. Sound travels faster in humid air because:
A) More density
B) Less density
C) Molecules are lighter (water vapor is lighter than nitrogen/oxygen)
D) Air pressure increases
✅ Correct Answer: C) Molecules are lighter
Explanation:
- C) ✔ Humid air has lighter molecules → faster sound speed.
Q23. Which instrument is used by doctors to hear heartbeat?
A) Microscope
B) Telescope
C) Stethoscope
D) Barometer
✅ Correct Answer: C) Stethoscope
Explanation:
- C) ✔ Stethoscope amplifies body sounds.
Q24. Which of the following affects loudness of sound?
A) Frequency
B) Amplitude
C) Wavelength
D) Medium
✅ Correct Answer: B) Amplitude
Explanation:
- B) ✔ Greater amplitude → louder sound.
Q25. Sound produced by a vibrating tuning fork is due to:
A) Expansion of air
B) Rarefactions and compressions in air
C) Changes in temperature
D) Chemical reactions
✅ Correct Answer: B) Rarefactions and compressions in air
Explanation:
- B) ✔ Vibrating fork sets air in compressions/rarefactions.
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