Download Section 3 Behavior of Waves

Ch 10
Section 3
Behavior of Waves
Reflection
  When a wave strikes an object and bounces back.
  Reflection in a mirror: Light hits your face and
bounces off to a mirror which bounces off and is
directed towards your eye.
Echo
  A reflection of sound waves
  Bats and dolphins use echo-location to navigate
through their environment.
Law of Reflection
  Incident beam- light hitting
mirror
  Reflected beam- light
bouncing off of mirror
  Angel of incidence is equal
to the angle of reflection.
Refraction
  Bending of a wave caused by the change in its
speed.
  Light moving through a gas to a solid can cause
refraction
Refraction of light in water
  Light travels at different speeds in water and air.
This causes refraction of the light.
  Objects appear in different places then they
actually are when this occurs
Diffraction
  When an object causes a wave to change direction
and bend around it.
  When waves pass around an object
Diffraction
  When a wave passes through a narrow opening and
spreads out afterwards.
Diffraction and wavelength
  If the object is smaller than the wavelength the
wave diffracts around it.
  If the object is larger than the wavelength the wave
does not diffract around it very much
Hearing around corners
  You can hear sounds around a corner due to the
diffraction that takes place with the sound waves.
  Sound waves are about 1 to 2 feet across; a door is
about 3 feet.
  This allows some of the sound waves to diffract
through a doorway.
  Light will not diffract around a corner due to the
short wavelength of light.
  Light has a λ of 300 to 900nm; this means light
does not diffract around corners of a hallway.
Diffraction of radio waves
  AM radio waves have shorter wavelengths than FM
radio waves; this means they can diffract around
buildings, hills and other objects.
  This gives AM stations better reception.
Interference
  When two or more waves overlap to form a new
wave.
Constructive interference
  Waves add together
  When the crests of two waves meet
Destructive interference
  Waves subtract from one another
  When the crest of one wave meets the trough of
another
Standing waves
  A wave pattern that
forms when waves
of equal
wavelength and
amplitude travel in
opposite directions
and interfere with
each other.
Standing waves in music
  Vibrations of a bow string and a violin create
standing waves from the vibrations.
  Flute creates a standing wave in a column of air.
Resonance
  Process by which an object vibrates by absorbing
energy at its natural frequencies.
  If enough energy is absorbed the object can vibrate
and break apart.