Production and Propagation of Sound - UNSOLVED PRACTICE SET

Q7. How is sound produced? Explain with the example of a stretched rubber band or a plucked guitar string.

Q8. What are compressions and rarefactions in a sound wave? How do they form as sound travels through air?

Q9. Prove experimentally or explain with reasoning that sound cannot travel through vacuum. Relate this to why we cannot hear sounds from explosions on the Moon.

Q10. Sound travels fastest in solids, then in liquids, and slowest in gases. Explain why, in terms of particle spacing and intermolecular forces.

Q11. Place your finger gently on your throat and speak aloud. What do you feel? What does this tell you about the production of sound in the human voice box?

Q12. Explain the difference between a transverse wave and a longitudinal wave. In which category does sound fall, and what evidence supports this?

Q13. Describe in detail how sound is produced and propagated through air. Your answer must cover:
(a) the role of vibration in producing sound,
(b) how the vibrating source creates alternating compressions and rarefactions, 

(c) how these disturbances travel outward as a wave,
(d) what actually moves — the particles or the disturbance, and
(e) why sound is called a mechanical wave and why it needs a medium.

Q14. A school bell rings at the end of a period.
(a) How is the sound produced by the bell?
(b) How does the sound reach students sitting at different distances in the classroom?
(c) Would the bell be heard if the school were in space (vacuum)?
(d) If you pressed your ear against the metal bench, would you hear the bell through the bench before hearing it through air? Explain.
(e) What type of wave is sound, and what is the direction of particle vibration relative to the direction of wave travel?

Q15. Compare the propagation of sound in solids, liquids, and gases. Your answer must include:
(a) the speed of sound in each medium (approximate values),
(b) the reason for the differences in terms of particle arrangement and bonding,
(c) a practical example of sound travelling through a solid (Indian example preferred),
(d) why divers can hear sounds from far away underwater, and
(e) why sound travels faster on a cold day than on a hot day (think about air density). 

Q16. A tuning fork vibrates at 440 Hz.
(a) What does 440 Hz mean physically — how many times does it vibrate per second?
(b) The speed of sound in air is 340 m/s. Calculate the wavelength of the sound produced. (Use: speed = frequency × wavelength)
(c) If the frequency is increased to 880 Hz (keeping speed constant), what happens to the wavelength?

Q17. A student in a factory notices that she can hear the sound of a distant machine through the metal pipes much earlier than through the air. The machine is 1700 m away. Speed of sound in air = 340 m/s, speed of sound in steel = 5100 m/s.
(a) How long does the sound take to reach her through air?
(b) How long through the steel pipe?
(c) What is the time difference?
(d) What conclusion can she draw about sound propagation?

Q18. A vibrating string on a sitar produces sound. The string vibrates 250 times per second.
(a) State the frequency of the sound produced.
(b) If the wavelength of this sound in air is 1.36 m, calculate the speed of sound in air.
(c) The same string is plucked harder — the amplitude increases. Does this change the frequency? Does it change the speed? What does it change? Explain each answer.