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# Waves

What are waves? Properties of Waves Interactions of Waves Seismic Waves
by

## Ashley Gremillion

on 6 April 2010

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#### Transcript of Waves

What are Waves?
wave
medium
material through which a wave travels
mechanical wave
waves that require a medium through which to travel
electromagnetic wave
waves that can travel without a medium
gases, liquids, solids
produced when a source of energy causes a medium to vibrate
types of mechanical waves
transverse
"across"
waves that move at right angles to the direction in which the waves travel
crest
the high part of a transverse wave
trough
the low part of a transverse wave
a disturbance that transfers energy from place to place
longitudinal
move the medium parallel to the direction in which the waves travel
compressions
where the coils are close together
rarefactions
parts where the coils are spread out or rarified
Properties of Waves
basic properties
amplitude
wavelength
frequency
speed
amplitude
the maximum distance that the particles of the medium carrying to wave move away from their rest position
in transverse waves
maximum distance the medium moves up or down from its rest position
in longitudinal waves
measure of how compressed or rarefied the medium the medium becomes
find by measuring the distance from the rest position to the crest or trough
dense compressions = large amplitude
wavelength
the distance between 2 corresponding parts of a wave
can measure distance from crest to crest or trough to trough
frequency
the number of complete waves that pass a given point in a certain amount of time
measured in:
hertz (Hz)
1 wave per second = 1 Hz
speed
how far the wave travels in a given length of time
speed = wavelength x frequency
frequency = speed / wavelength
wavelength = speed / frequency
Interactions of Waves
reflection
when an object or a wave hits a surface through which is cannot pass, it bounces back
refraction
bending of two waves due to a change in speed
when a wave enters a new medium at an angle, one side of the wave, changes speed before the other side, causing the wave to bend
bending only occurs when the wave enters the medium at an angle
examples: rainbow, see a fish under the water
diffraction
when a wave moves around a barrier or through an opening in a barrier, it bends and spreads out
interference
interaction between waves that meet
constructive interference
when waves combine to make a wave with a larger amplitude
destructive interference
two waves combine to make a wave with a smaller amplitude
Waves
Seismic Waves
waves produced by earthquakes
P waves, S waves, or surface waves
P WAVES
primary waves
longitudinal seismic waves
move faster than the other seismic waves and end up at distant points before the other types
compressions and rarefactions of rock inside the Earth
compress and expand the ground like a slinky
S WAVES
secondary waves
transverse seismic waves
shake the ground up and down and side to side as it moves through it
cannot travel through liquids
therefore, do not travel directly through the earth like P waves
Earth's core is...
liquid
SURFACE WAVES
combination of a longitudinal wave and a transverse wave that travels along the surface of a medium
move slower that P and S waves but cause the most severe ground movement
combine up and down and side to side motion, making the ground roll like ocean waves
tsunamis
huge surface waves on the ocean
caused from earthquakes underwater
the waves add upon each other as they reach shallow water
detecting seismic waves
seismograph
records the ground movements cause by seismic waves as they move through earth
placed at different locations around the world so when there is an earthquake...
P waves arrive before S waves
scientists measure the time between P and S waves and can tell how far away the earthquake was
Full transcript