Why is precious bird feather green?

The green color on the feathers of precious birds is not the natural color of feathers but because of the light effect created when dispersed on the surface of the feathers of birds.

The surface of feathers is randomly arranged into complex structures capable of dispersing light. It is this "pseudo-texture" effect that creates the blue color of the feathers of rare birds, such as the Indigo Bunting in the image below.

Indigo Bunting

Humans also have the ability to create the "color from the surface structure" effect as above, but both natural and human cannot produce red through this optical mechanism. A recent study has explained the phenomenon of eliminating large wavelengths and offering design materials that can produce red in everyone's eyes.

The colors made up of the surface structure are colors produced from micro-structures on the surface of the material. The light reflected from these surfaces will resonate, making some wavelengths (related to the separation between the components of the structure) become more prominent during light dispersion. If this structure has an orderly layout like crystals, the color material when reflecting light will create a "five-colored" surface - that is, the color changes depending on your perspective.

Blue Bird Blue Bird

Conversely, when the reflective structure is randomly arranged (such as bird feathers or crust on some purple beetles), the color will remain the same when viewed at any angle.

Professor Sofia Magkiriadou at Harvard University and colleagues found that the coloring surface does not depend on the perspective never creates red, orange and yellow colors. In order to find out the reason, they studied scattered light from a "photon glass" range of various plastic particles of different sizes. For surfaces with small size particles - the reflected light is mainly composed of blue wavelengths corresponding to the separation from one particle to another at an average level.

In contrast, with large particles, red light waves (due to dispersion) are expected to produce the dominant color. However, they are covered by a second peak of blue waves (including the light entering each plastic particle and reflecting directly). This reverse reflection is often found in ultraviolet rays, but occurs with visible wavelengths on large particles. Therefore, to create surfaces that can reflect red light, according to scientists at Harvard, humans will need to create surfaces that can avoid the aforementioned reflection.

Reference: Physics.