Physics / Unit 7: Waves and Sound
7.1 Types of Waves
Notes
A wave is a disturbance that carries energy from place to place without carrying matter along with it.
- Mechanical waves need a medium (solid, liquid or gas). Examples: sound, water waves, waves on a rope.
- Electromagnetic waves (like light) can travel through empty space.
- Transverse wave: the medium moves perpendicular to the wave direction (rope wave, light). It has crests and troughs.
- Longitudinal wave: the medium moves parallel to the wave direction (sound). It has compressions and rarefactions.
Practice
A cork bobs up and down as a water wave passes. What does the wave carry toward the shore?
Waves transfer energy; the water and cork mostly move up and down in place.
Sound is a longitudinal wave. This means the air molecules:
Longitudinal waves have particle motion along the travel direction.
Why can't sound travel through outer space?
Space is nearly empty, so there is no medium to vibrate.
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