Waves Sea is a term used to describe a confused mixture of waves that is often observed from ships.

Parts of a Wave Defined: Crest – highest point of a wave. Trough – lowest part of a wave; below the stillwater mark. Wave Height – vertical distance from crest to trough. Wave Length – horizontal distance from crest to crest. Wave Frequency – the # of wave crests that pass a fixed point per unit of time.

Labeling Parts of a Wave

Parts of a Wave Defined continued: Wave Period – the time in seconds that it takes for one complete wave to pass a fixed point. Wave Speed – the speed of a wave in a certain direction expressed as distance per unit of time.

Wave energy Many forms of energy are carried by waves: Heat, electricity, light, sound, and water All forms of energy can be transformed into work. Ocean waves break rock, carry sand away, and produce heat and sound when they slam into the shore. Energy in waves can be used to drive generators to produce electricity. We can measure the amount of energy in: Joules of work Kilocalories of heat Kilowatt hours of electricity If the energy is being transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt-hours is the product of the power in kilowatts and the time in hours. The kilowatt-hour is commonly used as a billing unit for energy delivered to consumers by electric utilities.

Wave energy The amount of energy in a wave depends on its height. The higher the wave, the more energy it releases. The energy per square meter is proportional to the square of its height.

Wind Waves Wind is the primary source of energy for waves. Most ocean waves are produced by the force of the wind. The force of the wind is influenced by: 1. Its duration, the length of time it’s been blowing 2. Its fetch (an old sailor’s term), the distance over which the wind is blowing. 3. Its average speed over the fetch

Understanding Movement of H2O Molecules: he waves on the surface of the water are neither longitudinal nor transverse. We can see in animation that red ball, which simulates the molecule of the water surface, moves in a circle path. So, the wave on the water surface is the superposition of transverse and longitudinal motions of the molecules. VIDEO

Calculating wave properties We can calculate the speed of a wave from its wavelength and period (time) using the formula: C = λ / t speed= wavelength/time Knowing that a wave has a wavelength of 20m and a period of 4 sec, we can calculate its speed. C= 20m/4sec C= 5 m/s

Wave frequency The frequency of a wave is the number of times it passes a given point in 1 second. The formula to calculate frequency is: ƒ=1/t

Where do waves break? Surf Zone – area near shore where waves break. Distance from shore where waves break depends on: Depth of water Length

How a wave breaks depends on: The steepness of the bottom slope Whether the slope is smooth or irregular Whether the bottom is composed of shifted sands or solid rock

Wave Properties Open ocean waves appear to change endlessly. Oceanographers and engineers who want to study waves must understand the basic properties of waves. Different waves have different speeds. Most waves travel at 20-40 mph.

Why do waves break? Steepness of bottom slope Composition of bottom: Shifting sands Solid rock

Force of Wind Duration – length of time it has been blowing. Fetch – the distance over which the wind is blowing.

Types of Breaking Waves: Spilling Breaker – Gently sloping coasts or flat coasts where the waves break slowly and over a long distance. Crest spills gently down the front of the wave. Wave energy is gradually released over time.

Types of Breaking Waves: Plunging Breaker – Formed when coast is moderately steep. Waves slow down more quickly, so crest curls way over the front of the wave and plunges down toward the base. As waves move towards the shore, they change from deep-water swells to shallow-water breaking waves. Constant pounding by waves erodes and changes coastal features.

Types of Breaking Waves: Surging Breaker – Very steep beach slope. Never really break; rush onto beach in a brief surge of water. Energy of wave is reflected.

Open Ocean Waves Ripple – small waves less than 1 foot in size Chop – Medium waves that come to a point at the crest. 1-3 feet in size Seas – Large waves associated with windy weather. 4 -10 feet in size Storm – Extremely large waves associated with tropical storm or greater winds. 6+ feet in size (winds exceeding 105 km/hr)

Interference patterns The wave patterns produced when two or more wave sets intersect are called interference patterns. Wave Reinforcement- exceptionally high waves when crests of two waves come together or very deep troughs when troughs combine. VIDEO