Propagation of Sound in Media MCQs Quiz | Class 9
This Class IX Science (Code 086) quiz covers Unit III: Motion, Force and Work, specifically focusing on the Propagation of Sound in Media. The questions test your understanding of sound transmission in solids, liquids, and gases, along with a comparative idea of speed in these media. Attempt all 10 MCQs, check your score, and download the PDF answer sheet for revision.
Overview: Propagation of Sound
Sound is a form of energy which produces a sensation of hearing in our ears. It is produced by vibrating objects. For sound to propagate from the source to the receiver, it requires a material medium like air, water, or steel. It cannot travel through a vacuum.
Key Concepts
- Mechanical Waves: Sound waves are mechanical waves because they need a material medium for their propagation.
- Longitudinal Nature: In air, sound travels as longitudinal waves consisting of compressions (high pressure) and rarefactions (low pressure). Particles oscillate parallel to the direction of propagation.
- Medium Dependency: The speed of sound depends on the properties of the medium (elasticity and density). Generally, sound travels fastest in solids, slower in liquids, and slowest in gases.
Speed of Sound Comparison
| State of Matter | Speed of Sound (Approx at 25 C) | Reason |
|---|---|---|
| Solids (e.g., Steel) | ~5960 m/s | Particles are packed tightly, transferring energy quickly. |
| Liquids (e.g., Water) | ~1498 m/s | Particles are less tight than solids but denser than gases. |
| Gases (e.g., Air) | ~346 m/s | Particles are far apart, transmission is slower. |
Quick Revision Notes
- Compression (C): Region of high pressure and high density.
- Rarefaction (R): Region of low pressure and low density.
- Vacuum: Sound cannot travel here (proven by Bell Jar Experiment).
Extra Practice Questions
- Why can astronauts not talk to each other directly on the Moon? (Ans: No atmosphere/medium).
- What physical quantity is transported by sound waves? (Ans: Energy, not matter).
- How does temperature affect the speed of sound in air? (Ans: Speed increases with temperature).
- Define a mechanical wave. (Ans: A wave requiring a medium to travel).
- Identify the wave type where particle motion is perpendicular to wave direction. (Ans: Transverse wave).
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