User:Renugadevi/Sandbox

Why blood appears green under water? Blood appears green at a certain depth underwater when illuminated by sunlight. The reason for this effect is not that the blood itself is changing color, but rather because the sunlight is filtered by the water. Above the water there will be a absorption spectrum, where it absorbs strongly in the blue, more weakly in green/yellow, and weakest at all in red. So blood mostly reflects red. But underwater, the sunlight that is transmitted is changed spectraly by absorption by the water. As light passes through water, its red component is transmitted faster than its green or blue components. At a certain depth, the green component becomes dominant over the red component, and thus when this filtered sunlight reflects from your blood, the reflected light will look green.