Common sense would suggest that the ocean should appear green, because about two meters below the surface of the ocean the water is filled with organisms and plants containing chlorophyll (a green pigment) which provide about 70% of oxygen quota to the life on Earth. However, the British physicist Lord Rayleigh (who isolated Argon gas in the Earth’s atmosphere in the year 1894) investigated this phenomenon and explained that the ocean appears blue because it reflects the color of the sky.
|C. V. Raman|
Years later in the year 1921, an Indian scientists C.V. Raman (photo, left) was returning via sea route from Britain after attending a physics related session. When he saw blue color of the ocean he remembered the Nobel Prize winner Lord Rayleigh’s explanation about it. It then occurred to Raman that if the ocean was indeed reflecting the color of the sky then after filtering the blue color with polarizer we should be able to see the real color of the sea. Subsequently he carried out this experiment, but even after filtering the blue color with polarizer the ocean looked blue. The explanation Raman derived was: Like the sky, the ocean’s molecules do not absorb blue light of the sun rays. Red, orange and yellow are absorbed by the water while the color blue is scattered. By scattering we mean the process by which radiation is absorbed and then reradiated by the material through which it passes. This is the same reason why the sky looks blue. For this explanation C.V. Raman was accorded Nobel Prize for physics in the year 1930.
The significance of this discovery was that it gave way to the new science of spectroscopy.