Key Idea #2: Waves are produced by vibrations in matter.

Matter is anything that has mass and takes up space.

A wave is a disturbance that transmits energy through matter and space.

http://www.isvr.soton.ac.uk/spcg/tutorial/tutorial/Tutorial_files/Web-basics-nature.htm

Mechanical waves are created when a source of energy causes a medium to vibrate.

The wave is the motion of a vibration.

FYI: In the above example the medium is a rope. Pick a

single particle and watch its motion. Notice that the medium itself doesn’t go anywhere.  

The individual atoms and molecules in the medium oscillate about their equilibrium (rest) position, but their average position does not change. 

As they interact with their neighbors, they transfer some of their energy to them. 

FYI The neighboring atoms in turn transfer this

energy to their neighbors down the line.  In this way the energy is transported

throughout the medium, NOT the particles of matter.

A vibration is a repeated back-and-forth or up-and-down motion.

http://www.isvr.soton.ac.uk/spcg/tutorial/tutorial/Tutorial_files/Web-basics-nature.htm

When molecules in matter vibrate, they cause other molecules to vibrate.

This causes waves to travel outward from the center of the vibration.

emusictips.com

An energy transfer takes place when molecules transfer the energy of motion to other molecules then return to their state of rest.

http://shadow.yak.net/15share.ehs.uen.org

Characteristics of Waves

Wavelength Frequency Amplitude

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A wavelength is the distance between two corresponding parts on

a wave.

turningthesolomonkey.com

The amplitude of a wave is a direct measure of its energy.

The greater the energy, the greater the wave’s amplitude is.

Amplitude

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The number of complete waves that pass given point in a certain amount of time.

The number of vibrations per second.

Example: If you make a wave in a rope so that 7 waves pass every second, it’s frequency is 7 waves per second.

Frequency

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Same amplitude Same amounts of energy

Different frequencies Different vibrations per second.

Same frequency Same number of vibrations per

second. Different amplitudes

Different amounts of energy.

Amplitude and Frequency

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These three waves have the same frequency but different amplitudes.

Amplitude determines the loudness of the sound.

The higher the amplitude, the louder the sound.

nasa.gov

These waves have different amplitudes and frequencies.

Amplitude and Frequency http://www.classzone.com/books/m

l_science_share/vis_sim/wslm05_pg18_graph/wslm05_pg18_graph.html

Frequency and Pitch High frequency = high pitch Low frequency = low pitch

Examples

Vibrating Ruler Short ruler=faster vibration=high frequency=high

pitch Long ruler=slower vibration=low frequency=low

pitch

String Instruments On string instruments thicker, heavier strings

vibrate more slowly than thinner strings The slower the vibration, the lower the pitch. The faster the vibration, the higher the pitch.

The Nature of Waves

How waves transfer energy:

When a tuning fork is placed in the water, ripples (waves) are seen coming away from the tuning fork in even rings.

http://www.google.com/imgres?imgurl=http://farm3.static.flickr.com/2589/3833077029_7c2329c700.jpg&imgrefurl=http://flickr.com/photos/zebraheart123/3833077029/&usg=__Z-v6J7yVPBhINHBpgaGZ83pRnz4=&h=328&w=500&sz=99&hl=en&start=70&zoom=0&tbnid=KSGsB6bPyo3odM:&tbnh=85&tbnw=130&prev=/images%3Fq%3Dtuning%2Bfork%2Bin%2Bwater%26um%3D1%26hl%3Den%26sa%3DG%26biw%3D1003%26bih%3D550%26tbs%3Disch:10%2C2024&um=1&itbs=1&iact=hc&vpx=165&vpy=137&dur=125&hovh=85&hovw=130&tx=116&ty=48&ei=FQmQTPezL4uInQfOrNW0DA&oei=AgiQTK3VMszsnQf34vy0DA&esq=12&page=5&ndsp=17&ved=1t:429,r:11,s:70&biw=1003&bih=550

When waves hit a beach, erosion takes place.

Ripples are left in the sand to show the reaction of the wave.

http://www.google.com/imgres?imgurl=http://farm4.static.flickr.com/3554/3574142548_733bc694c6_o.jpg&imgrefurl=http://flickr.com/photos/27998757%40N07/3574142548&usg=__JvJZwuBP3n5mWFxT5HOZ4AjQrf8=&h=683&w=1024&sz=699&hl=en&start=155&zoom=0&tbnid=5ebH6rCYsfEidM:&tbnh=100&tbnw=150&prev=/images%3Fq%3Dbeach%2Bsand%2Bripples%26um%3D1%26hl%3Den%26sa%3DG%26biw%3D1003%26bih%3D550%26tbs%3Disch:10%2C4171&um=1&itbs=1&iact=hc&vpx=523&vpy=327&dur=31&hovh=100&hovw=150&tx=78&ty=88&ei=7QyQTO-PLczAnAfmwPC0DA&oei=0wyQTMHsB9GTnQe908G0DA&esq=11&page=11&ndsp=15&ved=1t:429,r:2,s:155&biw=1003&bih=550

Seismic waves are vibrations that travel through the Earth carrying the energy of motion released during an earthquake.

When seismic waves travel through the Earth, the vibrations are transferred outward from the origin of the quake.

http://www.google.com/imgres?imgurl=http://www.physicalgeography.net/fundamentals/images/epicenter.gif&imgrefurl=http://www.physicalgeography.net/fundamentals/10m.html&usg=__GyFBnTPrAKTr9DHVTMwYp9bht4M=&h=304&w=372&sz=22&hl=en&start=0&zoom=1&tbnid=vS5JbAKvROSzCM:&tbnh=115&tbnw=141&prev=/images%3Fq%3Dearthquake%2Bseismic%2Bwaves%26um%3D1%26hl%3Den%26biw%3D1003%26bih%3D550%26tbs%3Disch:1&um=1&itbs=1&iact=rc&dur=94&ei=9Q6QTImjG8nonQfFyby0DA&oei=9Q6QTImjG8nonQfFyby0DA&esq=1&page=1&ndsp=17&ved=1t:429,r:1,s:0&tx=75&ty=53

Seismic waves are strong enough to cause the ground to tremble and buildings to shake and

crumble.

Strangevehicles.com

http://science.nationalgeographic.com/science/enlarge/earthquake-damage.html

Libcom.org