You're explaining to a younggster at the seashore why the water is cyan colored.The youngster points to the whitecaps of overturning waves and ask why they are white. what is your answer?
The color of deep water is due to the subtraction of the colors from light that penetrates deeply into the water, and is then scattered back out by small particles far beneath the surface of the water (typically meters to tens of meters). Sea foam of whitecaps reflects white light because is it a inhomogeneous mixture of water and air. Absorption does not play much of a role, because the layer of foam that the light penetrates before being scattered is too small to do much absorbing.
To explain why the water appears cyan and why the whitecaps of the waves appear white, let's start by understanding the concept of light and how it interacts with water.
1. Color of the Water: The water at the seashore may appear cyan or bluish-green due to the way it interacts with sunlight. When sunlight reaches the Earth's atmosphere, it contains all the colors of the visible spectrum. These colors have different wavelengths, and as sunlight passes through the atmosphere, it gets scattered by the molecules and particles present in the air.
2. Scattering of Light: The scattering process separates sunlight into different colors. Shorter wavelengths, like blue and cyan, are scattered more by the molecules in the air, while longer wavelengths, like red and yellow, are scattered less. This is why the sky appears blue during the day.
3. Reflection and Absorption: When sunlight reaches the ocean's surface, some of it is reflected back, while the rest is absorbed by the water. Water molecules absorb longer wavelengths, such as red and green, more readily, while shorter wavelengths, like blue and cyan, are less absorbed, resulting in that color being more visible.
So, the combination of scattered blue and cyan light from the sky and the absorbed colors in the water gives it a cyan or bluish-green appearance.
4. Color of Whitecaps: Now, let's talk about the whitecaps of the waves. When the wind blows over the ocean's surface, it creates turbulence, causing the formation of whitecaps. The white appearance of these foam crests is due to a different physical phenomenon known as foam or bubble scattering.
5. Foam Scattering: As waves break, the water becomes aerated, creating countless tiny air bubbles in the water. When light encounters these bubbles, it scatters in multiple directions due to the differences in refractive index between the air and water.
6. Scattering of All Colors: Unlike the scattering by the atmosphere that favors shorter wavelengths, the scattering within foam occurs equally for all wavelengths of visible light. As a result, the mixture of scattered light from these countless tiny air bubbles appears white to our eyes.
To summarize, the cyan color of the water is due to the scattering of shorter wavelengths of light like blue and cyan by the molecules in the air and the absorption of certain colors by the water itself. The white appearance of the whitecaps is caused by the scattering of all colors of light by countless tiny air bubbles present in the foam.