Why does the ocean appear blue and green?
This is a good question, and is related to the more commonly asked “why is the sky blue?” Partly, it’s because the sea reflects the blue sky (it isn’t as blue on an overcast day). But, as well as reflecting the sky, the sea is blue because it scatters the blue part of the light spectrum, and absorbs the red and yellow part., leaving the blue part of the spectrum, as well as part of the green (which is why deep water can appear bluish-green). This scattering effect is caused by the light waves striking the water molecules, causing them to vibrate and re-emit the light. Because the blue part of the spectrum has a shorter wavelength, it reacts with the light more; whereas the red and yellow part is absorbed (warming the water). Because the red part of the spectrum is absorbed, a red object looks black in deep water. The scattering effect is even stronger with ice; which results in the intense blue colour we see if we look down a crevasse in a glacier, or down a hole in the snow made by a
