physical science chapter 23
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Physical Science CHAPTER 23. Waves. Waves transmit energy!!!. Mechanical Vs. Electromagnetic Waves Waves. Mechanical Waves Need medium (gas, liquid, solid) Examples: Sound, water waves. - PowerPoint PPT PresentationTRANSCRIPT
Physical ScienceCHAPTER 23
Waves
Waves transmit energy!!!
Mechanical Vs. ElectromagneticWaves Waves
Mechanical WavesNeed medium
(gas, liquid, solid)
Examples: Sound, water waves
Electromagnetic WavesNo medium needed.
Example: Visible Light
(ROYGBIV), Ultraviolet, Infrared,Microwaves, etc…
http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html
3 main characteristics of all Waves1. Amplitude (high amplitude means high energy) 2. Wavelength (Unit: meters) 3. Frequency
Units: cycles/secWaves/sec 1/sHertz (Hz)
Frequency Example Problem
1. A boy standing on a dock counts 20 waves pass by in 5 seconds. What is the frequency of the waves?
f = #waves / time
20 waves / 5 seconds = 4 Hz
Frequency Example Problem #2
2. If the frequency of the waves is increased to 8 Hz, how many waves will pass by theboy in 2 seconds?
f = #waves / time
8 Hz = #waves / 2 seconds
8 Hz x 2 seconds = 16 waves
MECHANICAL WAVES (2 TYPES)
TRANSVERSE WAVES
LONGITUDINAL WAVES
SURFACE WAVES
http://www.gmi.edu/~drussell/Demos/waves/wavemotion.html
TRANSVERSE WAVE
LONGITUDINAL WAVE
SPEED OF WAVESspeed = frequency x wavelength
v = f x λ
Example #1A wave on a lake is traveling with a velocity of 8 m/s.the frequency is 2 Hz. What is the wavelength ofthis wave?
8 m/s = 2 Hz x λ
λ = 4 m
The Type Of Medium Determinesthe Speed of The WAVE!!
Higher Density = Slower Speed of Wave
Higher Elasticity = Faster Speed of Wave
THE 4 BASIC WAVE INTERACTIONS ARE:
1. REFLECTION2. REFRACTION3. DIFFRACTION
4. INTERFERENCE
1. REFLECTIONBouncing back of waves upon
reaching another surface.
THE LAW OF REFLECTION STATES THAT THE ANGLE OF INCIDENCE IS EQUAL TO THE
ANGLE OF REFLECTION.
2. REFRACTIONBending of waves due to a change in
speed.
3. DIFFRACTIONBending of waves around the edge
of an obstacle.
4. INTERFERENCE
1. CONSTRUCTIVE INTERFERENCEWhen waves combine and produce a wave that is greater than either of the waves alone.
2. DESTRUCTIVE INTERFERENCEWhen waves combine and produce a wave that is less than either wave alone.
Applet Interference by 3 wavessimultaneously.
http://www.chipr.sunysb.edu/eserc/ProjectJava/WaveInteractionApplet/
Another wave website to look at:http://www.howe.k12.ok.us/~jimaskew/pwave.htm
STANDING WAVES RESONANT FREQUENCY (or natural frequency)The frequency at which a standing wave occurs.
RESONANCEThe ability of an object to vibrate by absorbing energy of its own natural frequency. Video clip of the Tacoma Narrows Bridge November 1940http://www.gmi.edu/~drussell/Demos.html
NODESStationary points of a standing wave.
ANTINODESLoops of a standing wave where maximum oscillation of the medium occurs.