Shades of Blue

March 15, 2023


Photographer: Sandra Angelica 
Summary Authors: Sandra Angelica; Jim Foster

Shown above are various shades of blue captured at a beach resort in San Juan, La Union, Philippines. The swimming pool, sea and sky all exhibit a bluish color. Next to violet, blue is the shortest wavelength perceptible to the human eye -- wavelength range of approximately 450 to 495 nanometers. Although water transmits light of all the visible colors of the spectrum, its peak transparency is near 480 nanometers, thus it generally takes on a bluish color. Of course, factors such as water clarity, depth and roughness of the sea surface can greatly affect just how blue the water appears.

On the other hand, the sky is blue because of preferential scattering of sunlight by air molecules (Rayleigh scattering). Air molecules that are some 1,000 times smaller than wavelengths of blue light are the right size to scatter blue light more effectively than the other wavelength colors. For example, blue light is scattered 4 times more strongly than is red light. As a result, the sky looks blue. Photo taken on December 25, 2022.


San Juan, La Union, Philippines Coordinates: 16.6720, 120.3628

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