Waves & the EM Spectrum
A. Wave – a transfer of energy
 
a. In a wave, molecules pass energy on to neighboring molecules
 
b. Waves don’t transport matter
c. All waves are produced by something that  vibrates
d. A material through which a wave travels is a  medium . i. It can be  solid, liquid, or gas .
Not all waves need a medium through which to travel. ii. What is an example of this type of wave?
 
B.  Mechanical waves  need  a medium to travel. They  cannot  travel  through empty space.
Do sound waves travel faster  through gases or liquids?
 
 
Sound Waves through Gas
Try this:  Smack your hand down on your desk.  It’s pretty loud, huh? Now, lay your head down on your desk and smack again.  Any louder?  WHY?
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Mechanical waves can only travel through a medium.
a. Transverse wave –  matter is displaced at right  angles as energy is transferred
 
 
Example:  Water waves
 
b. Longitudinal Wave – Matter is displaced in the same direction as the energy is transferred
 
 
Example: Sound Waves
a. They carry different            amounts of  energy
b. They travel at different  speeds
 
Doppler Effect
 
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i. Transverse -
ii. Longitudinal -
B.  Wavelength  – distance between a point on a wave and the nearest point just like it SI Unit:  m
C.  Frequency  – Number of wavelengths that pass a fixed point in one second SI Unit:  Hz
b. As frequency increases,  wavelength decreases.
D.  Wave Velocity  –  how fast the wave travels a. Velocity = wavelength x frequency SI Unit: m/s
b. Light vs. Sound
c. Sound waves travel faster in:
d. Light waves travel faster in:
E.  Amplitude  – measure of energy in a wave
vs. a. The more energy a wave carries, the greater the amplitude.
b. Amplitude of transverse wave:
c. Amplitude of longitudinal waves:
A.  Reflection  occurs when a wave strikes an object and bounces off of it.
a.  All  types of waves can be reflected
 
b.
 
 
 
 
 
 
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B  Refraction  is the bending of a wave caused by a change in its speed.
 
 
 
 
a. The greater the change in speed is, the  more  the wave bends. Wave Refraction
C.  Diffraction  is when an object causes a wave to change  direction and bend around it.
 
Diffraction
D. Interference – the ability of two or more waves to  combine  and form a new wave
a. Waves  add  together
b. Waves  subtract  from each other
 
E. Resonance – the ability of any object to  vibrate  by absorbing energy at its natural frequency
Wine Glass Resonance
The End
 
 
Helpful reminders for the test: Differences b/w experimental variables (Ind, Dep, Constant, Control) Understand velocity & acceleration Newton’s 3 Laws of Motion Plotting Ind. & Dep. Variables Energy

Mechanical Waves