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The Powerful Pulse of Sound Waves

Sound waves are a fundamental type of mechanical wave that play a crucial role in our daily lives as well as in physics and engineering applications. From hearing speech and music to medical imaging and underwater navigation, sound waves form the basis of many natural and technological processes. In physics, sound waves are studied under wave motion because they exhibit properties such as reflection, refraction, interference, diffraction, and resonance.

Sound waves are produced when an object vibrates and sets the surrounding medium into oscillatory motion. Since sound requires a material medium for propagation, it cannot travel through a vacuum. Depending on the medium—solid, liquid, or gas—the speed and nature of sound propagation vary. In gases like air, sound waves propagate as longitudinal waves, where particles of the medium oscillate parallel to the direction of wave travel, forming alternate regions of compression and rarefaction.

Key characteristics of sound waves include frequency, wavelength, amplitude, speed, pitch, loudness, and intensity. Frequency determines the pitch of sound, while amplitude governs its loudness. These parameters are central to solving numerical and conceptual problems in competitive examinations. The speed of sound depends on the elasticity and density of the medium and increases with temperature in gases.

Sound waves also form stationary waves in confined systems such as organ pipes and strings, leading to the formation of nodes and antinodes. This phenomenon explains resonance, beats, and harmonics, which are essential concepts in musical acoustics and wave theory. Applications of sound waves extend to ultrasonics, SONAR, medical diagnostics, and industrial testing, highlighting their importance beyond theoretical physics.

Table of Contents

30 Sound Waves MCQs with Answers

1. The distance between the successive nodes is

A. 4λ
B. 2λ
C. λ
D. 2λ
Answer: C

2. An air column of length 20 cm resonates with a tuning fork of frequency 500 Hz. The speed of sound is

A. 100 m/s
B. 200 m/s
C. 400 m/s
D. 1000 m/s
Answer: C

3. A tuning fork of frequency 256 Hz makes 5 beats/s with a guitar string. When tension is increased, beats reduce to 2/s. The original frequency was

A. 258 Hz
B. 254 Hz
C. 261 Hz
D. 251 Hz
Answer: D

4. Waves produced in the prongs and stem of a tuning fork are

A. Transverse in both
B. Longitudinal in both
C. Transverse in prongs, longitudinal in stem
D. Longitudinal in prongs, transverse in stem
Answer: C

5. When an open organ pipe is dipped in water up to half its height, its frequency will

A. Half
B. Double
C. Remain same
D. Four times
Answer: C

6. A closed organ pipe of length 20 cm resonates with a tuning fork. The frequency is

A. 300 Hz
B. 350 Hz
C. 375 Hz
D. 415 Hz
Answer: D

7. Difference between second overtone of closed pipe and first overtone of open pipe is 100 Hz. Fundamental frequency of closed pipe is

A. 200 Hz
B. 150 Hz
C. 100 Hz
D. 50 Hz
Answer: C

8. Speed of sound is 330 m/s. If third harmonic in an open pipe is 450 Hz, the pipe length is

A. 3.3 m
B. 1.1 m
C. 2.2 m
D. 4.5 m
Answer: B

9. Ratio of first resonance lengths of open pipe to closed pipe using same tuning fork is

A. 1:1
B. 2:1
C. 1:2
D. 3:1
Answer: B

10. Length of closed pipe whose fundamental frequency equals that of an open pipe of length 60 cm is

A. 20 cm
B. 24 cm
C. 28 cm
D. 30 cm
Answer: D

11. A closed organ pipe vibrating in third overtone has

A. 3 nodes & 3 antinodes
B. 3 nodes & 4 antinodes
C. 4 nodes & 3 antinodes
D. 4 nodes & 4 antinodes
Answer: D

12. Which statement is NOT true for an open pipe?

A. Open ends are antinodes
B. Odd harmonics present
C. All harmonics present
D. Pressure change maximum at ends
Answer: D

13. Fork A makes 4 beats/s with 320 Hz fork. After filing, 4 beats/s again heard. Frequency of A before filing was

A. 328 Hz
B. 316 Hz
C. 324 Hz
D. 320 Hz
Answer: B

14. Speed of sound is 330 m/s and frequency is 165 Hz. Distance between two successive nodes is

A. 2 m
B. 1 m
C. 4 m
D. 0.5 m
Answer: B

15. In an open pipe vibrating in fundamental mode, pressure variation is maximum at

A. l/4 from ends
B. Middle of pipe
C. Ends of pipe
D. l/8 from ends
Answer: B

16. SONAR uses

A. Infrasonic waves
B. Audible sound waves
C. Ultrasonic waves
D. All of these
Answer: C

17. Amplitude of sound waves is measured in units of

A. Pressure
B. Distance
C. Time
D. Speed
Answer: B

18. When pitch increases, which quantity increases?

A. Intensity
B. Loudness
C. Wavelength
D. Frequency
Answer: D

19. Ripples in water due to loud music are caused by

A. Reflection
B. Refraction
C. Reverberation
D. Resonance
Answer: D

20. Velocity of sound where two wavelengths 4.08 m & 4.16 m produce 40 beats in 12 s is

A. 282.8 m/s
B. 175.5 m/s
C. 353.6 m/s
D. 707.2 m/s
Answer: D

21. Reflection of sound from denser medium returns compression as

A. Crest
B. Trough
C. Compression
D. Rarefaction
Answer: C

22. Speed of sound in air

A. Increases with temperature
B. Increases with pressure
C. Increases with humidity
D. Decreases with humidity
Answer: C

23. Beats are formed due to

A. Dispersion
B. Reflection
C. Refraction
D. Interference
Answer: D

24. Maximum displacement = 0.1 cm, frequency = 300 Hz. Maximum velocity is

A. 60 cm/s
B. 30 cm/s
C. 6 cm/s
D. 60 m/s
Answer: A

25. Distance between 6 successive nodes is 85 cm in Kundt’s tube. Speed of sound is

A. 330 m/s
B. 350 m/s
C. 340 m/s
D. 300 m/s
Answer: B

26. Fork A produces 5 beats/s with 480 Hz. After adding wax, beats become 2/s. Original frequency was

A. 475 Hz
B. 482 Hz
C. 478 Hz
D. 485 Hz
Answer: D

27. Fork produces 4 beats/s with 510 Hz and 6 beats/s with 512 Hz. Frequency is

A. 518 Hz
B. 506 Hz
C. 510 Hz
D. 514 Hz
Answer: B

28. Speed of sound in water at 20°C is approximately

A. 330 m/s
B. 800 m/s
C. 1500 m/s
D. 500 m/s
Answer: C

29. Compared to audible sound, ultrasound has

A. Higher speed
B. Higher frequency
C. Longer wavelength
D. Higher speed and frequency
Answer: D

30. Loudness of sound depends on

A. Velocity
B. Amplitude
C. Frequency
D. Frequency & velocity
Answer: B

sound waves

Conclusion: Sound Waves

Sound waves represent a vital link between abstract wave theory and real-world phenomena. The study of sound waves provides a deep understanding of how energy is transmitted through matter via oscillatory motion of particles. Unlike electromagnetic waves, sound waves are mechanical in nature and rely entirely on the presence of a medium, making their behavior strongly dependent on material properties such as density and elasticity.

Concepts such as beats, resonance, standing waves, harmonics, pitch, and loudness demonstrate how sound waves interact with boundaries and with each other. These sound waves principles explain the functioning of musical instruments, tuning forks, resonance tubes, and organ pipes. The formation of nodes and antinodes in stationary waves highlights that while energy transfer ceases in such systems, oscillations continue locally, a concept frequently tested in physics examinations.

The practical importance of sound waves is immense. Ultrasonic waves are used in medical imaging, flaw detection in materials, and underwater exploration through SONAR. Knowledge of sound wave behavior enables advancements in communication technology, architectural acoustics, and noise control engineering. Understanding how sound behaves in different environments helps in designing efficient audio systems and improving sound quality.

From an academic perspective, sound waves provide an excellent framework to apply mathematical reasoning, graphical interpretation, and physical intuition. Mastery of sound wave concepts strengthens problem-solving skills and builds a foundation for advanced topics in waves, optics, and quantum physics. In conclusion, sound waves are not only essential for understanding physical acoustics but also serve as a gateway to appreciating the broader principles of wave motion that govern many natural and technological systems.

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