1 Waves Physical Science Chapter 15

2 Waves Rhythmic disturbances that carry energy through matter or space.

3 Medium What a wave travels through  Solid  Liquid  Gas Mechanical waves – require a medium

4 Electromagnetic waves Do not need a medium to travel through

As a wave travels Each wave front gets bigger  Like the ripples from dropping a rock in a lake Each wave front carries the same amount of energy The energy is spread out over a larger area as the wave gets farther from its source 5

Source of waves Usually a vibration  Like vocal cords or speakers 6

Simple Harmonic Motion A type of vibration where energy changes form between kinetic and potential, but total energy is conserved.  A mass on a spring  A clock pendulum 7

Discuss Why can supernova explosions in space be seen but not heard on Earth? 8

9 Transverse wave The medium moves at right angles to the direction the wave travels. Crests – the highest points Troughs – the lowest points

10 Transverse wave ls/waves/wavetypes.htm#trans ls/waves/wavetypes.htm#trans

11 Longitudinal waves The matter vibrates in the same direction as the wave is traveling. Also called compressional waves.

12 Longitudinal waves ls/waves/wavetypes2.htm ls/waves/wavetypes2.htm

13 Parts of a longitudinal wave Compression – the area where the coils are packed together Rarefaction – the area where the coils are spread apart.

Surface waves Occur at a boundary between two different mediums, like water and air. Particles move both perpendicularly and parallel to the direction of wave travel. The particles make an elliptical or circular shape. 14