Waves
• Anatomy of wave
– Wave- transmission of energy through matter
– Longitudinal wave- matter oscillates in same
direction of energy transmission
– Transverse wave- matter oscillates perpendicular
to direction of energy transmission
– Orbital wave- matter oscillates in a circular path as
energy passes (ocean waves!)
• Anatomy of wave
– H:L - ration of wave height to wave length
– Speed = wavelength/ period
• Wave causes
– Disturbing force- cause waves
– Restoring force- resist waves
• Wave characteristics
– Deepwater waves – occur in water that is deeper
than half their wavelength; bottom does not affect
the wave
– Transitional waves- occur when depth is between
½ and 1/20 the wavelength
– Shallow water waves- occur when depth is less
than 1/20 the wavelength; bottom affects wave
• Wave size affected by:
– Wind speed
– Wind duration
– Fetch- surface area over which wind blows
• Surf and breaking waves
– Why do waves break?
• Transitional waves slow down because of bottom;
shortens wavelength causing wave height to increase
• When wave’s H:L ratio passes 1:7 , the crest is moving
faster than trough; causes wave to break with the crest
toppling forward
• Types of Breakers
– Spilling Breaker- top of wave tumbles and slides down
front of wave; gently sloped beaches
– Plunging breaker- curled on top; moderately steep beaches
– Surging Breaker- surges unbroken (destructive), steep walllike beaches
• Wave interactions
– Refraction- bending of waves as they approach
shore
– Diffraction- when waves pass an obstacle, energy
shifts forming a new wave pattern
– Reflection- wave bounces back when hits obstacle
• http://www.tectonics.caltech.edu/outreach/a
nimations/tsunami_youtube.html
• Destructive waves
– Storm surge- forms when high winds push water
against the shore
– Tsunami- results from sudden displacement of
water caused by landslide, falling iceberg, volcanic
eruption or earthquake
• Always shallow water waves because wavelength is so
long that no ocean is deep enough for them to be
deepwater waves
• Do not destroy ships because wavelength is so long that
ships rise and fall without noticing