What are waves?
- Waves are forward movement of fluid due to oscillation of particles caused by a force.
- Despite a large amount of energy it may carry forward, there is little actual forward motion of individual water particles in a wave,
- Waves can occur on the free surface of all water bodies.
- Caused by gravity, wind, underwater volcanoes earthquake, landslides or explosions and by the movement of a ship or a fish.
- Here confined to seawater oscillations caused by frictional drag caused by a wind force over the sea surface.
- Wind waves vary from small ripples to huge rogue waves.
- Waves can travel thousands of miles before reaching land.
how are they formed?
- As wind blows over water it tries to drag water surface with it.
- The surface cannot move as fast as air, so it rises.
- When it rises, gravity pulls the water back’
- Momentum of falling waters reaches below the surface.
- Water pressure from below pushes falling water up again.
- This tug of war between gravity and water pressure cause the up-down movement of fluid.
- There is also a small component of to and fro motion of water in a wave.
- The wave may travels forward for thousands of mile but but the water particles don’t.
- Otherwise all the oceans would empty onto the shore!!!!!
- A wave transfers energy from one water molecule to the next causing water particles to move in a circular pattern as shown by the bottle movement on a water surface.
- This circular motion of water particle does not occur over the entire depth of water.
- There are multiple circles of water particle movements where circles grow smaller with increasing depths as seen in the next diagram to the right.
- At a depth about equal to half the wavelength, the motion stops.
As they propagate across the open ocean, wind-generated waves maintain a constant speed, which is unaffected by depth until they reach shallow water