The Mystery of Colored Objects Underwater: How Colors Change and Why

When we look at a colored object above water, we perceive its true color. However, when the same object is submerged, it often appears differently. This phenomenon is due to the unique way light behaves in water and how our human visual system perceives it. Understanding colored objects underwater involves examining the light spectrum, water absorption, and the concepts of light refraction.

The Role of Light Spectrum and Human Vision

Our perception of color is limited compared to that of many other animals. Humans can only see a narrow band of the light spectrum, while species like bees and birds can perceive a broader range. When light meets water, it undergoes several changes that affect what we see. Water breaks up the light, causing colors to appear different when observed underwater compared to above the water's surface.

When we perceive a colored object, we are seeing the ambient light, such as sunlight, reflecting back from that object. Certain wavelengths of light are reflected, giving the object its color. All other wavelengths are absorbed by the object. The reflection of a specific color is determined by the atomic arrangement of particles, such as electrons, within the substance, which selectively absorb and re-emit photons based on quantum laws. Tomatoes, for example, appear red because the pigment atoms in their skin absorb photons of all energies except those corresponding to red wavelengths, which they reflect.

The Impact of Light Absorption in Water

When light passes through water, some of its wavelengths are absorbed by the water molecules, preventing them from being reflected back off submerged objects. Water absorbs longer frequencies, such as red and orange, while transmitting shorter frequencies, like blue and green. This results in a beam of light traveling through water losing its red hue and appearing blue. Consequently, objects that appear red above water will lose this color when submerged, and the deeper they go, the more color is lost.

Understanding Water's Translucency and Refraction

Water is translucent, meaning it slowly filters, absorbs, or reflects light. At a depth of 1 inch, colors remain the same. Beyond this, the light changes. At 8 feet, everything appears with a bluish tinge. By 80 feet, all is blue with hints of other colors, and beyond this depth, there is no light at all.

When light is seen at an angle, some of it reflects, making a portion of the water appear white. Some light penetrates and returns through the surface, causing refraction or bending of the light. This distortion of light causes objects to appear distorted in the water. The color of an object underwater is influenced by its depth and the water's clarity. Factors such as clean, chlorinated water (like a swimming pool), saltwater (ocean), or muddy water also affect the perceived color.

The tinting toward blue occurs due to the absorption or reflection of longer wavelengths first. This change in wavelengths leads to refraction or bending of light as it passes through water or glass.

Conclusion

The phenomenon of colored objects appearing differently underwater is fascinating and multifaceted. It involves the optical properties of water, the limitations of human vision, and the physics of light behavior. By understanding these factors, we gain insight into the visual world of aquatic environments and the complex nature of how colors evolve in such settings.