Waves

Question 1

wave

Answer 1

Disturbance caused by the movement of energy from a
source through some medium (solid, liquid, gas)
no movement of mass
classified by disturbing force, restoring force, and wavelength

Question 2

progressive wave

Answer 2

a wave of moving energy in which energy moves in one direction across the surface of the medium

Question 3

orbital wave

Answer 3

a progressive wave in which particles of the medium move in closed circles
water particles move in orbits, transmitting energy from particle to particle
motion is negligible below a depth of 1/2 the wavelength
at that depth, orbits are only 1/23 the diameter of those at the surface

Question 4

wave height

Answer 4

Vertical distance between a wave crest and adjacent trough

Question 5

wavelength

Answer 5

Horizontal distance between two successive crests (or troughs)

Question 6

wave period

Answer 6

Time it takes for a wave

to move a distance of one wavelength

Question 7

wave frequency

Answer 7

Number of waves

passing a fixed point per second

Question 8

celerity

Answer 8

speed
C=L/T
longer wavelength = faster wave
only depends on the local water depth

Question 9

deep water waves

Answer 9

Waves moving through water deeper than half their wavelength (L<2D)
→ The wave does not “feel” the bottom; orbits are circular
only capillary and wind waves CAN be deep water waves

Question 10

shallow water waves

Answer 10

Waves moving through water shallower than 1/20 their original wavelength (L>20D)
→ The wave does “feel” the bottom; orbits are not circular (elliptical to flat)

Question 11

formation of wind waves

Answer 11

Wind waves grow from capillary waves
- Capillary waves form as wind friction stretches the water surface and as surface tension tries to restore
its smoothness
- Capillary waves are always nearly present on the ocean (“ripples”)
- Capillary waves contribute to the transfer of wind energy into the water
→ As a result capillary waves progressively grow into wind waves (L > 1.74 cm)
Wind waves become larger if the wind continues to blow and waves remain in deep water (L < 2D)
- If winds get faster, more energy is input to the wave whose height grows
→ Wavelength (L) and wave period (T) increase proportionally

Question 12

sea

Answer 12

Irregular peaked waves in the area of wind-wave formation

→ Chaotic surface is formed by simultaneous wind waves of many wavelengths, periods, and heights

Question 13

wave steepness

Answer 13

Ratio of wave height to wavelength (H/L)
→ Wind waves have a wave steepness of maximum 1:7
→ If wave steepness gets greater, then waves break (whitecaps)

Question 14

fetch

Answer 14

The uninterrupted distance over which the wind blows without a significant change in direction

Question 15

fully developed sea

Answer 15

The maximum wave size theoretically possible for a wind of a specific strength,
duration, and fetch

Question 16

Dispersion

Answer 16

Waves with longer wavelengths move faster
→ These waves leave the area of formation sooner than their smaller counterparts
→ The process of wave separation is called dispersion

Question 17

swell

Answer 17

Mature wind waves of one wavelength that form orderly undulations of the ocean surface

Question 18

surf beat

Answer 18

Big “sets” of waves expected by surfers between calm intervals
→ Results from constructive and destructive interferences of wind waves

Question 19

rogue/freak wave

Answer 19

Unexpected huge wave that suddenly erupt from a moderate sea
→ Higher wave than the theoretical maximum wave capable of being sustained in a fully developed sea
→ Results from constructive interference

Question 20

surf

Answer 20

Turbulent mass of agitated water rushing shoreward during and after the break

Question 21

surf zone

Answer 21

Region between the breaking waves and the shore

Question 22

Slope of the bottom

Answer 22

plunging wave - a breaking wave which forms an air-filled tube
→ Gradually shoaling bottoms can sap waves of their strength

Question 23

Composition of the bottom

Answer 23

Energy of wave lost through interaction against bottom

→ Rough bottoms will extract more energy than smooth bottoms

Question 24

refraction

Answer 24

Slowing and bending of progressive waves in shallow water
→ The part of the wave line in shallow water slows down
→ The part of the wave still in deeper water continues at its original speed
→ The wave line bends (refracts)
- The refracted waves break in a line almost parallel to the shore

Question 25

diffraction

Answer 25

Propagation of a wave around an obstacle
→ Unlike wave refraction which depends on a wave’s response to a change in speed
→ Wave diffraction depends on the interruption of the wave trains by an obstacle

Question 26

reflection

Answer 26

Occurs when waves “bounce back” from an obstacle they encounter
→ If incoming wave strikes the obstacle at a right angle, the wave energy is reflected back parallel to
the incoming wave
→ More commonly, waves approach the shore at an angle, causing wave energy to be reflected at an
angle equal to the angle at which the wave approached the obstacle
→ Reflected waves can cause interference with oncoming waves

Question 27

internal waves

Answer 27

Subsurface wave forming at the boundary between water layers of different densities
→ Occurs in the ocean at the base of the pycnocline
- Internal waves are generated by wind energy, tidal energy and ocean currents
- Internal waves move more slowly than waves at the surface because the density difference between the two media is smaller
mix nutrients and trigger blooms
affect submarines and oil platforms

Question 28

tsunami

Answer 28

Long wavelength (up to 200 km), shallow-water progressive wave caused by the rapid
displacement of ocean water
- Tsunami can be caused by sudden, vertical movement of Earth along faults (seismic sea waves), landslides, icebergs
falling from glaciers, volcanic eruptions, asteroid impacts, etc

Question 29

tsunami propagation

Answer 29

As shallow water waves, tsunami are affected by the contour of the bottom and are commonly refracted
→ Wave is guided by mid-ocean ridges
→ Where depths are shallower, waves are slower, and energy becomes focused