Sound Waves: 17 flashcards
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1. What is sound?
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Sound is a form of energy that produces the sensation of hearing in our ears.
2. How is sound produced?
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Sound is produced when a body vibrates. Vibrations create disturbances in the medium, which travel as waves.
3. Can sound travel in vacuum? Why or why not?
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No, sound cannot travel in vacuum because sound waves require a material medium (solid, liquid, or gas) for propagation. On the moon, there is no medium, so sound cannot be heard.
4. Does light require a medium to travel?
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No, light does not require any material medium for propagation and can travel through vacuum.
5. What is a longitudinal wave?
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A longitudinal wave is a wave in which the particles of the medium vibrate about their mean positions in the direction of propagation of sound. Sound travels in air as longitudinal waves.
6. What are compression and rarefaction?
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Compression is a region where particles of the medium are closer together (high pressure). Rarefaction is a region where particles are spread apart (low pressure). They are produced alternately as a sound wave travels.
7. What is the relation between velocity (V), frequency (f), and wavelength (λ) of a sound wave?
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V = fλ, where V is the velocity of sound, f is the frequency, and λ is the wavelength.
8. If the frequency of a sound wave is 500 Hz and its wavelength is 0.66 m, what is its speed?
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V = fλ = 500 × 0.66 = 330 m/s.
9. In which medium does sound travel fastest: solid, liquid, or gas?
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Sound travels fastest in solids, then liquids, and slowest in gases. For example, sound travels faster in iron than in air or water.
10. What is the effect of temperature on the speed of sound in air?
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The speed of sound in air increases with an increase in temperature. Warmer air allows sound to travel faster.
11. Why do we see lightning before we hear thunder?
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Because the speed of light is much greater than the speed of sound in air. Light travels almost instantly, while sound takes time to reach us.
12. What are infrasonic, sonic, and ultrasonic frequencies?
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Infrasonic: frequencies below 20 Hz. Sonic: frequencies between 20 Hz and 20,000 Hz (audible range). Ultrasonic: frequencies above 20,000 Hz.
13. Give one application of ultrasonic waves.
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Ultrasonic waves are used in medical imaging (e.g., sonography), cleaning, and detecting flaws in materials.
14. What is the difference between ultrasonic and supersonic?
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Ultrasonic refers to sound waves with frequencies above 20,000 Hz. Supersonic refers to speeds greater than the speed of sound (e.g., supersonic aircraft).
15. Why does a vibrating tuning fork cause a suspended table tennis ball to jump?
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The vibrating prongs of the tuning fork transfer mechanical energy to the air, creating sound waves. These waves carry energy and push the ball, causing it to move away.
16. What happens to the particles of a medium when a sound wave passes through it?
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The particles vibrate about their mean positions, but they do not travel along with the wave. The disturbance (energy) moves forward, not the particles themselves.
17. What type of medium is required for sound propagation to be efficient?
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The medium should be frictionless so that there is no loss of energy during propagation. Materials like air, water, and iron transmit sound well, while blankets and thick curtains absorb sound.
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