Nature of Sound MCQs Quiz | Class 9
Class IX Science (Code 086), Unit III: Motion, Force and Work. This quiz covers the topic Nature of Sound, specifically focusing on sound as a mechanical wave and the requirement of a medium for propagation. Attempt these 10 MCQs to test your understanding, then submit to check your score and download the PDF answer sheet.
Understanding Nature of Sound
Sound is a form of energy which produces a sensation of hearing in our ears. In Class 9 Science, Unit III, we learn that sound is produced by vibrating objects. The matter or substance through which sound is transmitted is called a medium. It can be solid, liquid, or gas. Sound moves through a medium from the point of generation to the listener.
Key Concepts
- Mechanical Wave: Sound waves are characterized as mechanical waves because they require a material medium (like air, water, or steel) for their propagation.
- Vacuum: Sound cannot travel through a vacuum. This is demonstrated by the famous Bell Jar experiment. Without air particles to vibrate and pass on the energy, sound cannot move.
- Propagation: When an object vibrates, it sets the particles of the medium around it vibrating. The particles do not travel all the way from the source to the ear; they simply displace adjacent particles and return to their original position.
Speed of Sound in Different Media
The speed of sound varies depending on the nature of the medium. Generally, sound travels fastest in solids, slower in liquids, and slowest in gases.
| Medium State | Example | Relative Speed |
|---|---|---|
| Solid | Steel / Iron | Fastest (approx 5000-6000 m/s) |
| Liquid | Water | Moderate (approx 1400-1500 m/s) |
| Gas | Air | Slowest (approx 340 m/s) |
Quick Revision Points
- Sound is produced by vibration.
- Sound needs a medium to travel; it cannot travel in a vacuum.
- Sound waves are mechanical waves.
- The particles of the medium transport energy, not matter.
Extra Practice Questions
1. Why do astronauts use radio devices to talk on the moon? (Ans: No atmosphere/medium exists on the moon).
2. What happens to the air particles when a vibrating object moves forward? (Ans: They are pushed together creating compression).
3. Can sound travel through water? (Ans: Yes, as it is a liquid medium).
4. Which travels faster, light or sound? (Ans: Light travels much faster).
5. What do we call the region of low pressure in a sound wave? (Ans: Rarefaction).
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