What process causes the blue color of ocean water?

• A. Molecular Scattering
• B. Refraction
• C. Absorption by dissolved salts
• D. Sediment deposition

Answer: (A)

When sunlight enters ocean water, the light interacts with the water molecules and gets scattered. Shorter wavelengths (like blue) scatter more readily than longer wavelengths, so more blue light is redirected toward our eyes from the water. That increased back-scattered blue light is what gives the ocean its characteristic blue color. Refraction bends light but doesn’t selectively color it; absorption by dissolved salts would affect color differently and isn’t what makes the water blue in clear conditions; sediment deposition would make the water look murkier rather than distinctly blue. So the blue hue primarily comes from molecular scattering of light.