Chapter 11 Waves n Wave a disturbance that

Chapter 11 Waves

n Wave – a disturbance that transfers energy through matter or space. n Medium – the material a wave passes through

n The energy travels, NOT the medium! n A wave does NOT carry matter with it! It just moves the matter as it goes through it.

n Mechanical Waves- Waves that can only pass through matter. n Examples: sound and seismic waves.

n Electromagnetic Waves- Waves that can travel through empty space. n Examples: light, radiowaves, microwaves

Types of Waves n Transverse Waves: waves that move the medium at right angles to the direction of waves are traveling.

Types of Waves n Longitudinal (Compressional) Waves: the particles move parallel to the direction the wave is moving, “pushpull” waves.

Wave animations n Waves travel through the medium without actually moving the medium with it. Basically the medium stays put while the wave moves some distance n http: //www. acs. psu. edu/drussell/Demos/waves/w avemotion. html

Parts of a Wave n Transverse wave: Crest- the highest point of the wave n Trough- the lowest point of the wave n

Parts of a Wave n Longitudinal (compressional): compression- where the medium is close together n rarefaction- where the medium is spread apart n

n Amplitude- how far the medium moves from rest position (where the wave isn’t moving). n n in a transverse wave – the height away from the “rest” position. Remember the highest point is the crest and the lowest point is the trough.

n Amplitude- how far the medium moves from rest position (where the wave isn’t moving). n in a longitudinal wave - it is measured by how close or far apart the particles are. n n of how compressed or rarefied the medium becomes. The greater the amplitude, the greater the energy of the wave.

n Wavelength – the distance between two corresponding parts of a wave.

n n Frequency – the number of waves that go past a point in one second; unit of measure is hertz (Hz). The higher the frequency the more energy in the wave n n n 10 waves going past in 1 second = 10 Hz 1, 000 waves go past in 1 second = 1, 000 Hz 1 million waves going past = 1 million Hz

Wave speed n The speed depends on the medium the wave is traveling through. n n We calculate this by: n n n Sound travels fastest through solids and slowest in air. Wave speed= frequency x wavelength Rearrange for frequency and wavelength in your notes. Units: n n n speed – meters/second (m/s) frequency – Hz (1 Hz = 1 wavelength per second) wavelength – meters (m)

Think about it… n decreases As wavelength increases, frequency _. increases n As wavelength decreases, frequency __ __.