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Electromagnetic WavesNo medium needed.
Example: Visible Light
(ROYGBIV), Ultraviolet, Infrared,Microwaves, etc…
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
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
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