Waves

Question 1

What are the three types of waves?

Answer 1

1. Capillary
2. Wind
3. Internal

Question 2

What is the equation for wave steepness?

Answer 2

H/L

Question 3

What is the wave period?

Answer 3

Time for one wave length

Question 4

What is the typical wave period in deep water?

Answer 4

10-12 seconds

Question 5

What is the typical wave period in shallow water?

Answer 5

6-8 seconds

Question 6

What is wave frequency?

Answer 6

cycles per second

Question 7

What is a fully developed sea?

Answer 7

Provided the fetch is extensive enough and the wind blows at a constant speed for long enough, an equilibrium is reached in which energy is being dissipated by the waves at the same rate as the waves receive energy from the wind. This equilibrium results in a sea state known as a fully developed sea.

Question 8

What is the fetch?

Answer 8

The unobstructed distance of the sea over which the wind blows

Question 9

Why does a fully developed sea rarely happen?

Answer 9

Because the wind speed is variable so waves with uniform size are rare. In reality a fully developed seas consists of a range of wave sizes known as the wave field

Question 10

What is Swell?

Answer 10

Long wavelength, regular waves with visible long crests. They have been generated elsewhere and travel far from their place of origin

Question 11

How are wind waves formed?

Answer 11

Friction occurs between water and air they are 2 fluids of different densities and this generates a shear stress. A transfer of energy occurs in the surface levels of the ocean as a result of the frictional forces

Question 12

How much of the energy generated goes into the wave?

Answer 12

90%

Question 13

How much of the energy generated goes into moving the actual body of water forward?

Answer 13

10%

Question 14

For Jeffrey’s Sheltering Model what must be true?

Answer 14

1. Wind speed exceeds wave speed
2. Wind speed exceeds 1m/s
3. There are steep enough waves present to provide a sheltering effect
4. The process is carrying on until the wave cannot accept any further energy

Question 15

What is White Capping?

Answer 15

The removal of excess energy via friction

Question 16

What is sea state measured on?

Answer 16

The Beaufort Scale

Question 17

How do you calculate wave speed in deep water where the depth is greater than ½L

Answer 17

length/time

Question 18

In shallow water, what is wave speed proportional to?

Answer 18

length and depth

Question 19

In deep water, where depths are less than L/20 what is wave speed proportional to?

Answer 19

depth only

Question 20

What is constructive interference?

Answer 20

2 waves with similar wavelengths come into contact with one another doubling the amplitude and reducing the trough

Question 21

What is destructive interference?

Answer 21

One wave is the opposite to the other, they cross and cancel each other out leading to irregular frequencies and amplitude distribution

Question 22

What happens when waves reach the shore?

Answer 22

Friction occurs with the seabed and structures. There is a transfer from KE to PE. Wavelength decreases and wave height increases. When they become unstable they break.

Question 23

What are wave reflection and refraction?

Answer 23

Waves may be reflected back out at the same angle; this is especially seen on headlands with SW’y winds.

Wave refraction is the turning motion; the outer part of the wave is moving faster than the inner part of the waves. Refraction creates a bending of the waves as a result of wave shoaling

Question 24

What is a Rouge wave?

Answer 24

A wave much larger and steeper than the significant wave height

Question 25

What is a Kelvin wave?

Answer 25

A progressive wave affected by the Earths rotation. In the Northern hemisphere the crest of the wave slopes up to the Right looking in the direction of wave travel. A Kelvin wave travelling down a channel therefore has greater amplitude on the right-hand shore