Waves Light

1
Waves (Light Sound)

• Unit VII

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Types of Waves

• Transverse Wave Causes the particles of the
  medium to vibrate perpendicularly to the
  direction of motion of the wave.
• Longitudinal Wave Causes the particles of a
  medium to move parallel to the direction of the
  wave.

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Types of Waves

• Surface Waves A mixture of transverse and
  longitudinal waves.
• Wave Pulse A single disturbance that travels
  through a medium.
• Traveling Wave A source that is vibrating with
  simple harmonic motion will produce a continuous
  traveling wave.

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The Measure of a Wave

• Period (T) The shortest time interval during
  which the motion repeats itself.
• Frequency (f) The number of complete vibrations
  per second measured at a fixed location.
  Frequency is measured in hertz.
• One hertz (Hz) is one vibration per second or f
  1 / T

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Example

• A sound wave has a frequency of 262 Hz. What is
  the time between successive wave crests?
• f 262 Hz
• T 1 / 262 Hz
• T .00382 s

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The Measure of a Wave

• Wavelength ( ?) The shortest distance between
  points where the wave pattern repeats itself.
• Crest (C) Are the high points of each wave
  motion.
• Troughs (T) Are the low points of each wave
  motion.
• Eq v ? / f

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Wave Parts

• Wave Parts

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Example

• A sound wave with frequency 262 Hz has a
  wavelength of 1.29 m. What is the velocity of the
  sound wave?
• f 262 Hz
• ? 1.29 m
• v (1.29m)(262 Hz)
• v 338 m/s

9
Waves

• Amplitude the maximum displacement from the rest
  or equilibrium position.
• Often a wave moves from one medium to another.
  Light moves from air into water. Suppose a wave,
  called the incident wave, reaches the boundary of
  a medium. Part of the energy carried by the
  incident wave continues on in the new medium as a
  wave of same frequency. This wave is called the
  transmitted wave. Part of the energy moves
  backward from the boundary was a wave in the old
  medium. This wave is called the reflected wave.

10
Superposition of Waves

• What happens when two or more waves travel
  through a medium at the same time?
• Each wave affects the medium independently.
• Principle of Superposition The displacement of a
  medium caused by two or more waves is the
  algebraic sum of the displacements caused by the
  individual waves.

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Superposition of Waves

• Interference The result of the superposition of
  two or more waves.
• Constructive Interference When the wave
  displacements are in the same direction. The
  result is a wave with larger amplitude than any
  of the individual waves.
• http//id.mind.net/zona/mstm/physics/waves/interf
  erence/constructiveInterference/InterferenceExplan
  ation2.html
• Destructive Interference Two pulses with equal
  but opposite amplitudes. As the two pulses
  overlap, the displacement of the medium at each
  point in the overlap is reduced. When the pulses
  are at the same location, the displacement is
  zero.

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Standing Waves

• Node One point in the medium that is completely
  undisturbed at all times. At a node, the medium
  is never displaced.
• Antinode One point that undergoes the greatest
  displacement. Its maximum amplitude is equal to
  the sum of the amplitudes of the two pulses.

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Standing Waves

• Standing Wave Has stationary nodes and
  antinodes. It is the result of identical waves
  traveling in opposite directions.

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Reflection of Waves

• Normal The direction of the barrier is also
  shown by a line drawn at a right angle to it.
• Angle of Incidence The angle between the
  incident ray and the normal.
• Angle of Reflection The angle between the normal
  and the reflected ray.
• Law of Reflection States that the angle of
  incidence is equal to the angle of reflection.

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Refraction of Waves

• Refraction The ? of wave direction _at_ the
  boundary between 2 media.

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Diffraction Interference of Waves

• Diffraction The spreading of waves around the
  edge of a barrier.

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Quiz

• Quiz