Waves

							                       Waves



 Waves are everywhere. Sound waves, visible light waves,
radio waves, microwaves, water waves, sine waves, cosine
  waves, earthquake waves, waves on a string, and slinky
   waves and are just a few of the examples of our daily
                 encounters with waves.
                    Waves

   A wave can be described as a disturbance
    that travels through a medium from one
    location to another location.
        The Nature of a Wave
   Consider the slinky
    – When a slinky is stretched from end to end and is held
      at rest, it assumes a natural position known as the
      equilibrium or rest position.
        The Nature of a Wave
   Consider the slinky
    – To introduce a wave into the slinky, the first coils are
      displaced or moved from its equilibrium or rest
      position. The coils might be moved upwards or
      downwards, forwards or backwards; but once moved, it
      is returned to its original equilibrium or rest position.
        The Nature of a Wave
   Consider the slinky
    – The act of moving the first coils of the slinky in a given
      direction and then returning it to its equilibrium
      position creates a disturbance in the slinky.
        The Nature of a Wave
   Consider the slinky
    – If the first coil of the slinky is given a single back-and-
      forth vibration, then we call the observed motion of the
      disturbance through the slinky a pulse. A pulse is a
      single disturbance moving through a medium from one
      location to another location.
       The Nature of a Wave
   Consider the slinky
    – The repeating and periodic disturbance which moves
      through a medium from one location to another is
      referred to as a wave.
    – A medium is a substance or material which carries the
      wave.
    – Waves are said to be an energy transport
      phenomenon.
             Types of Waves
   A Transverse wave is a wave in which particles
    of the medium move in a direction perpendicular
    to the direction which the wave moves.




                                    Slinky Demo
             Types of Waves
   A Longitudinal wave is a wave in which particles
    of the medium move in a direction parallel to the
    direction which the wave moves.




                                    Slinky Demo
             Types of Waves
   A Surface wave is a wave in which particles of
    the medium undergo a circular motion. Surface
    waves are neither longitudinal nor transverse.




                                    Video in 3 slides
                 Surface Wave

   Water Waves
    – A wave moving across the surface of an ocean, lake,
      pond or other body of water. The waves are created by
      some form of a disturbance, such as a rock thrown into
      the water or a boat moving through the water. The
      water wave has a crest and a trough and travels from
      one location to another.
                 Surface Wave
   In longitudinal and transverse waves, all the
    particles in the entire bulk of the medium move in
    a parallel and a perpendicular direction
    (respectively) relative to the direction of energy
    transport. In a surface wave, it is only the particles
    at the surface of the medium which undergo the
    circular motion.
              Surface Wave

   Another view
Properties of Waves
         Properties of Waves
   A Transverse Wave
    – The crest of a wave is the point on the medium which
      exhibits the maximum amount of positive or upwards
      displacement from the rest position. The trough of a
      wave is the point on the medium which exhibits the
      maximum amount of negative or downwards
      displacement from the rest position.




                                                 Slinky Demo
                                                 Next
        Properties of Waves
   A Transverse Wave
    – The amplitude of a wave refers to the maximum
      amount of displacement of a particle on the medium
      from its rest position on a wave.




                                                Slinky Demo
        Properties of Waves
   A Longitudinal Wave
    – A compression is a point on a medium through which a
      longitudinal wave is traveling which has the maximum
      density. The amplitude of a longitudinal wave is a
      measure of how compressed the medium becomes.




                                         Slinky Demo
                                         Next
         Properties of Waves
   A Longitudinal Wave
    – A rarefaction is a point on a medium through which a
      longitudinal wave is traveling which has the minimum
      density.




                                           Slinky Demo
         Properties of Waves
   Wavelength
    – The wavelength of a wave is simply the length of one
      complete wave cycle.
         Properties of Waves
   Frequency
    – The frequency of a wave is the number of complete
      waves that pass a given point in a certain amount of
      time.
    – Frequency is expressed in Hertz (abbreviated Hz) where
      1 Hz = 1 cycle/second.
         Properties of Waves
   Speed
    – The speed of a wave is how far a wave travels in one
      unit of time, or the distance divided by the time.

    – Speed = Wavelength * Frequency

    – Or…Frequency = Speed / Wavelength
Interaction of Waves
        Interaction of Waves
   Reflection
    – When a wave hits a surface through which it
     cannot pass, it bounces back
        Interaction of Waves
   Angle of Incidence
    – The angle of incidence is the angle between the
      incoming wave and an imaginary perpendicular line to
      the surface.
      Interaction of Waves
Angle of Incidence.
 The angle of reflection is the angle between the reflection
 and the imaginary line.
        Interaction of Waves
   Refraction
    – Refraction is seen when a wave moves from one
      medium to another at an angle, it changes speed as it
      enters the second medium causing it to bend.




                                             Aquarium Demo
      Interaction of Waves
 Diffraction
  – Diffraction is seen when a wave passes a barrier or
    moves through a hole in a barrier, it bends and spreads
    out.




                                    Wave Tank Demo
     Interaction of Waves
 Interference
 – When two or more waves meet
     Interaction of Waves
 Constructive           Interference
 – When two or more waves combine to make a wave with
   a larger amplitude.
      Interaction of Waves
 Destructive         Interference
  – When the amplitudes of two or more waves combine to
    produce a wave with a smaller amplitude.
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