# Waves

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```					                       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
– 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
– 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
– 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
– 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
– 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.

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.

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.

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.

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.

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.

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.
Blank

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