13.1. WAVES

Waves are actually the energy, not the water as such, which moves across the ocean surface. Water particles only travel in a small circle as a wave passes.

Waves represent energy moving through the oceans rather than the water itself. When a wave passes, water particles move in circular paths, meaning that while the wave energy travels forward, the individual water molecules mostly move up and down within a limited area.

Imagine a person on a trampoline. As they bounce, they are moving up and down, but they don’t leave the trampoline's spot. Similarly, water particles behave in this bouncing manner when waves pass by.

Wind provides energy to the waves. Wind causes waves to travel in the ocean and the energy is released on shorelines.

Waves are formed by the wind blowing over the surface of the sea. The energy from the wind transfers to the water, creating waves that then travel across the ocean. As these waves approach the shore, they release their energy, often leading to breaking waves and surf.

Think of how you blow on a surface of water in a glass; the air from your breath creates small ripples or waves. In the same way, wind creates larger waves on the ocean's surface.

As a wave approaches the beach, it slows down due to the friction occurring between the dynamic water and the sea floor. When the depth of water is less than half the wavelength of the wave, the wave breaks.

When waves travel, they encounter the seabed as they get closer to the shore. This interaction causes the bottom part of the wave to slow down, while the top keeps moving fast. When the depth of water decreases and can't support the wave anymore, it forms a breaking wave.

Imagine riding a bicycle on a road that gradually narrows. As you reach the end, you slow down because of the friction with the ground, just like waves slow down and break as they hit the shoreline.

Waves continue to grow larger as they move and absorb energy from the wind. Most of the waves are caused by the wind driving against water.

As waves travel over longer distances, they pick up energy from the wind. This causes the waves to become larger and stronger, as they travel across vast expanses of ocean until they finally reach shore.

Think of how a surfer waits for a large wave. The longer they wait, the bigger and more powerful the wave becomes, just like wind energizes waves as they travel.

Wave crest and trough: The highest and lowest points of a wave are called the crest and trough respectively. Wave height: It is the vertical distance from the bottom of a trough to the top of a crest of a wave. Wave amplitude: It is one-half of the wave height.

Waves have specific characteristics that can be measured. The crest is the tallest point of a wave, and the trough is the lowest. The height is measured from the trough to the crest, while amplitude is half of the total height, representing the energy of the wave.

You can think of waves like hills. The top of the hill is akin to the crest, while the dip is like the trough. Measuring how high the hill is gives you the wave height, just like measuring from the trough to the crest.

Wave period: It is merely the time interval between two successive wave crests or troughs as they pass a fixed point. Wave speed: It is the rate at which the wave moves through the water, measured in knots. Wave frequency: It is the number of waves passing a given point during a one-second time interval.

The period of a wave tells us how often waves pass a given point, while wave speed tells us how fast those waves move across the water. Frequency gives an idea of how many waves arrive in a second, which can indicate wave conditions.

Consider watching a train passing by. If trains are frequent, they seem to come every few seconds (high frequency), while if one comes after a long wait, that’s low frequency. Similarly, waves can be closely spaced or far apart.

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