GENERAL PROPERTIES OF WAVES INTRODUCTION TO WAVES.
-
Upload
jason-farmer -
Category
Documents
-
view
225 -
download
0
Transcript of GENERAL PROPERTIES OF WAVES INTRODUCTION TO WAVES.
GENERAL PROPERTIES OF GENERAL PROPERTIES OF WAVESWAVES
INTRODUCTION TO WAVES
INTRODUCTION TO WAVES
Throwing a pebble into a pond… Tsunami (26 Dec 2004)tsunami-04.wmv
What is a wave?
Spreading of disturbance from one place to another.
The source is a vibration or oscillation.Energy is transferred from one point to
another WITHOUT physical transfer of any material between the two points
Two types of waves…
Mechanical – waves that require a medium in which to travel
Electromagnetic (EM) – do not require a medium – think light!
Two types of Mechanical waves:
Type of Mechanical wave depends on the direction of the displacement of the wave itself.
TRANSVERSE – displacement is perpendicular to starting position
LONGITUDINAL – displacement is parallel to starting position
Comparing the two types:
THE WAVE THE WAVE GAME!!GAME!!
ROPE WAVES
Flash Animation of Rope Waves
What do you observe about the wave motion? How is it similar to the human wave in the wave game?
transverse_waves.swf
Transverse Waves
Transverse waves travel in a direction PERPENDICULAR to the direction of the vibrations.
Transverse Waves
Some Examples:water waves rope waveselectromagnetic waves (example: light)
Test Yourself!
Rhonda sends a pulse along a rope. How does the position of a point on the rope, before the pulse comes, compare to the position after the pulse has passed?
The Slinky Coil
What do you notice about the direction of the vibrations and the direction of the wave?longitudinal_waves.swf
LONGITUDINAL WAVES
Longitudinal waves travel in a direction PARALLEL to the direction of vibrations.
Example: Sound
candles and sound waves.mov
Longitudinal Waves
Compressions are Where the coils/particlesAre squeezed together.
Rarefactions are Where the coils/particlesSpread out.
Compression & Rarefactions
Compression Rarefaction
Challenge
Describe how the fans in a stadium must move in order to produce a longitudinal stadium wave.
One more question….
A wave is transporting energy from left to right. The particles of the medium are moving back and forth in a leftward and rightward direction. What type of wave is this?
What if the particles move upward and downward?
THE WAVE THE WAVE GAME!!GAME!!
Part 2Part 2
Crests and Troughs
Crests: points of maximum displacement on a wave Troughs: points of minimum displacement on a wave
Distancealong rope
displacement
CREST CREST
TROUGH
AMPLITUDE (A)
Maximum Displacement from the rest or central position.
SI unit metre (m)displacement
distance along rope
crest crest
trough
amplitude
amplitude
Wavelength (λ)
The distance between two successive points of the same phase. Example: distance between two crests. SI unit: metre (m).
displacement
distance along rope
crest crest
trough
λ
amplitude
amplitude
Parts on a Longitudinal Wave
Think of compressions as the crests Think of rarefactions as the troughs
Frequency (f)
Number of complete waves generated per second (or number of cycles/oscillations per second)
SI unit: hertz (Hz)
Period (T)
Time taken to generate one complete wave (or to complete one cycle)
SI unit: second (s)
fT
1
As f increases, T decreases
Relationship between T and f
Putting everything together
Try this!wave_terms.swf
SUMMARY
FOOD FOR THOUGHT
In space films, we often hear the sound of the engine of the spaceship as the zoom past each other in outer space. We even hear the spaceship firing lasers at one another. What is seriously wrong in the films?
FOOD FOR THOUGHT
Why don't incoming ocean waves bring more water on to the shore until the beach is completely submerged?
FOOD FOR THOUGHT
How will the motion of water waves change as they move from deep to shallow water? How about from shallow to deep water?
(Hint: Consider the speed of the waves)