![]() ![]() On a large body of water (the ocean or a very large lake) with a fetch of 139 km and winds of 37 km/h, the waves will develop fully in 10 hours the average amplitude will be around 1.5 m and average wavelength around 34 m. In a situation where the fetch is short (say 19 km on a lake) and the wind is only moderate (19 km/h), the waves will develop fully within 2 hours, but they will remain quite small (average amplitude about 27 cm, wavelength 8.5 m). The typical sizes and speeds of waves in situations where they have had long enough to develop fully are summarized in Table 17.1. Figure 17.2 The parameters of water waves The important parameters of a wave are its wavelength (the horizontal distance between two crests or two troughs), its amplitude (the vertical distance between a trough and a crest), and its velocity (the speed at which wave crests move across the water) (Figure 17.2). The stronger the wind, the longer it blows, and the larger the area of water over which it blows (the fetch), the larger the waves are likely to be. This potentially undescribed cidippid ctenophore was seen floating gracefully in the water column during dive 10 of the Deep Connections 2019 expedition.Waves form on the ocean and on lakes because energy from the wind is transferred to the water. This helps them evade predators when there is nowhere to hide. Since there is no red light available, red animals here will appear gray or black, making them nearly invisible to other organisms. At this depth, few, if any, red light waves reflect back to one’s eye. Red and black animals are common in the deep ocean. Blue light penetrates much farther, so blue objects are more visible in the deep. Red and orange light waves have less energy, so they are absorbed near the ocean surface. It absorbs the other colors (all of which are present in white light). For example, an object we see as red in white light appears that way because it reflects longer, less energetic red light waves. The wavelength of light that reflects off an object is the color we see. ‘Photic’ is a derivative of ‘photon,’ the word for a particle of light. Although some sea creatures depend on light to live, others can do without it. The ocean is divided into three zones based on depth and light level. ![]() Meanwhile, some other deep-sea animals have completely lost their ability to see. This is one of their amazing adaptations that helps them survive. They can be 10 to 100 times more sensitive to light than human eyes. Some deep- sea organisms’ eyes have evolved to improve their vision in low light. Light conditions affect how much both humans and organisms see. This sunless realm is known as the aphotic zone. Once we reach about 1,000 meters depth, light from above has disappeared entirely. Very little light from the surface penetrates between 200 and 1,000 meters, in what’s known as the dysphotic or twilight zone. A view of a mussel bed near New Zealand at 100 m depth, lit only by sunlight. Because blue and violet light waves have more energy, they travel deeper through water. In water, colors with lower energy, such as reds, oranges, and yellows are filtered out quickly. Colors with shorter wavelengths, like those on the blue and violet end of the spectrum, have more energy than colors with longer wavelengths. Wavelength shortens as you move in sequence from red to violet light across the spectrum. Red light has the longest wavelength in the visible spectrum and violet has the shortest wavelength. Each visible color has its own wavelength, or distance between two waves. When all of these colors are combined together, they appear white as white light. Sunlight contains all of the colors of our visible spectrum- red, orange, yellow, green, blue, and violet (ROYGBV). This means the light waves that make up violets, indigo and blue have higher energy levels than the yellow, orange and red.
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