The ocean appears blue to us because of a combination of several factors. This is why different oceans, seas, lakes, and other bodies of water can be different shades of blue or even other colors completely.
1. Different materials absorb and reflect wavelengths of light differently –
Light is composed of several different wavelengths. We see different visible wavelengths as different colors. These colors are called the visible spectrum. As light hits a body of water, it penetrates the surface. Blue wavelengths of light penetrate the deepest. The others are absorbed by the water molecules more quickly. Because blue travels further, when light is reflected, more blue comes out of the water than other colors.
2. Particles in the water help to reflect different colors of light –
Minerals and other small particles help to reflect blue light in the ocean. Some particles, especially plant and algae growth, reflect other colors. The red sea is red because of an abundance of red algae. Many bodies of water appear green due to green plant life growing in the water. In rivers, different colors of sediment are swept up in the water, and this gives rivers different colors. Often, after a storm, many oceans or other bodies of water can appear brownish because the ocean currents have stirred up large amounts of sand.
3. Water surfaces reflect light that is already present –
Water is blue partially because the sky is blue. Since the sky creates so much blue light, a lot of this light is reflected off the surface of the water. We are all aware that we can see ourselves in still bodies of water. This mirror action also works for the sky itself, giving water a blue hue.
Posted 2440 day ago