WAVES AND

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Chapter 14 WAVES AND ENERGY TRANSFER
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• What you will learn
• You will determine how waves transfer energy
• You will describe wave reflection and discuss its
  practical significance

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• Why its important
• Waves enable the suns energy to reach Earth and
  make possible all communication through sound.
• Because light waves can be reflected, you are
  able to see the world around you and even read
  these very words.
• Knowledge of behavior of waves is essential to
  the designing of bridges and many other
  structures.

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• State Standards Addressed
• Waves Waves have characteristic properties that
  do not depend on the type of wave. As a basis for
  understanding this concept
• Students know waves carry energy from one place
  to another.
• Students know how to identify transverse and
  longitudinal waves in mechanical media, such as
  springs and ropes, and on the earth (seismic
  waves).
• Students know how to solve problems involving
  wavelength, frequency, and wave speed.
• Students know sound is a longitudinal wave whose
  speed depends on the properties of the medium in
  which it propagates.
• Students know radio waves, light, and X-rays are
  different wavelength bands in the spectrum of
  electromagnetic waves whose speed in a vacuum is
  approximately 3108 m/s (186,000 miles/second).
• Students know how to identify the characteristic
  properties of waves interference (beats),
  diffraction, refraction, Doppler effect, and
  polarization.

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Chapter 14 Waves and Energy Transfer
I. Wave Properties A. Classes of Waves (wave- a
rhythmic disturbance that carries energy
through matter or space) 1. Mechanical
Waves a. Requires a medium (water, air,
springs, etc.) b. Includes sound waves,
water waves, waves that move down rope
or spring, etc.      
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2. Electromagnetic Waves a. No medium   b.
Consists of coupled changing magnetic and
electric fields that move through space at the
speed of light (3.00 x 108 m/s) 186,000 miles/s
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B. Types of Waves (2) 1. Transverse wave- a wave
that vibrates perpendicular to the direction of
the wave motion  
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2. Longitudinal waves-disturbance is in the same
direction as, or parallel to, the direction of
the wave motion  a. Includes sound waves b.
Surface waves have characteristics of both
transverse and longitudinal waves
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C. Measuring a Wave 1. Speed a. Find speed
of pulse (single bump or disturbance) b.
First measure displacement of wave peak
(?d) c. Then divide by the time interval (?t)
to find speed d. In most waves (both
transverse and longitudinal, speed depends only
on the medium through which the waves move    
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2. Amplitude- the maximum displacement from its
position of rest, or equilibrium a. depends on
how the wave is generated, but not on its
speed. b. More work has to be done to generate a
wave with a larger amplitude.    
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3. Wavelength- The shortest distance between
points where the wave pattern repeats itself. a.
Troughs- low points (troughs are spaced by one
wavelength) b. Crests- high points (crests are
spaced by one wavelength) c. Greek letter
lambda ?, represent wavelength.    
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4. Period and Frequency (only apply to continuous
waves) a. Period (T)- the time needed to repeat
one complete cycle of motion b. Frequency
(f)- number of complete oscillation each second.
1). Measured in hertz. (one hertz one
oscillation per second)   2). Equation        
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c. Both period and frequency of a wave depend
only on its source. They do not depend on the
waves speed or the medium d. More equations
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II. Wave Behavior A. Waves at Boundaries 1.
Speed of wave depends only on the properties
of the medium, not the waves amplitude or
frequency.   a. Water waves- depth of the water
affects speed b. Sound waves in air-
temperature affects speed c. Waves in
spring- depends on the springs rigidity and
its mass per unit length.  
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2. Incident wave- wave that strikes a boundary 3.
Reflected wave- energy of incident wave reflected
backward creating returning wave  
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B. Superposition of Waves- two or more waves
combine to form a new wave of less or greater
amplitude 1. Wave Interference- can be either
constructive or destructive a. Destructive
interference- the superposition of waves with
equal but opposite amplitudes
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1). When pulse meets, displacement is zero. 2).
Point N, which doesnt move at all is called a
node   
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b. Constructive Interference- occurs when wave
displacements are in the same direction 1).
Results in wave that has an amplitude larger
than any of individual waves 2). Point A has the
largest displacement is called the antinode.    
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2. Standing Waves- produced when two sets of
waves of equal amplitude and wavelength pass
through each other in opposite directions.     
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C. Refraction- the change in direction of waves
at the boundary between two different media  D.
Diffraction- the spreading of waves around the
edge of a barrier