Rarely, a moonbow, lunar rainbow or nighttime rainbow, can be seen on strongly moonlit nights. In addition, the effect can be artificially created by dispersing water droplets into the air during a sunny day. The rainbow effect is also commonly seen near waterfalls or fountains. These include not only rain, but also mist, spray, and airborne dew.Įruption of Castle Geyser, Yellowstone National Park, with double rainbow seen in the mist
Rainbows can be caused by many forms of airborne water. More modernly, the rainbow is often divided into red, orange, yellow, green, cyan, blue and violet. The initialism is sometimes referred to in reverse order, as VIBGYOR. For colours seen by the human eye, the most commonly cited and remembered sequence is Isaac Newton's sevenfold red, orange, yellow, green, blue, indigo and violet, remembered by the mnemonic Richard Of York Gave Battle In Vain, or as the name of a fictional person ( Roy G. Any distinct bands perceived are an artefact of human colour vision, and no banding of any type is seen in a black-and-white photo of a rainbow, only a smooth gradation of intensity to a maximum, then fading towards the other side. Rainbows span a continuous spectrum of colours. Even if an observer sees another observer who seems "under" or "at the end of" a rainbow, the second observer will see a different rainbow-farther off-at the same angle as seen by the first observer. Indeed, it is impossible for an observer to see a rainbow from water droplets at any angle other than the customary one of 42 degrees from the direction opposite the light source. Thus, a rainbow is not an object and cannot be physically approached. Image of the end of a rainbow at Jasper National ParkĪ rainbow is not located at a specific distance from the observer, but comes from an optical illusion caused by any water droplets viewed from a certain angle relative to a light source. This is caused by the light being reflected twice on the inside of the droplet before leaving it. In a double rainbow, a second arc is seen outside the primary arc, and has the order of its colours reversed, with red on the inner side of the arc. This rainbow is caused by light being refracted when entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it. In a primary rainbow, the arc shows red on the outer part and violet on the inner side. However, the observer normally sees only an arc formed by illuminated droplets above the ground, and centered on a line from the Sun to the observer's eye. Rainbows caused by sunlight always appear in the section of sky directly opposite the Sun.
The rainbow takes the form of a multicoloured circular arc. It is caused by refraction, internal reflection and dispersion of light in water droplets resulting in a continuous spectrum of light appearing in the sky. The shadow of the photographer's head at the bottom of the photograph marks the centre of the rainbow circle (the antisolar point).Ī rainbow is an optical phenomenon that can occur under certain meteorological conditions. These otherworldly blue ferns glow up the base of the blue-tinged Pandoran vein pods which absorb methane from the air and collecting it in globular structures float away and explode high in the sky upon reaching maximum capacity.Double rainbow and supernumerary rainbows on the inside of the primary arc. This is hypothesized to be an adaptation against sun damage from intense sun spots that occasionally flicker across the plants in their low light forest understorey habitat. The intense blue of these ferns is caused by coiled cellulose nanostructures in their upper leaf surface which scatter and reflect light in blue wavelengths instead of green. Their iridescent blue-green color shifts with the light and viewing angle and is not due to a blue pigment, but a phenomenon called structural iridescence, also found in a few animals, like the also seen in the blue-green tips of peacock tail feathers and the wings of Morpho butterflies. siamense has shorter, elliptical leaves.īlue is an extremely rare color in plants and animals and the origin of the blue on these ferns even moreso. thailandicum has elongated strap-shaped leaves, whereas M. Microsorum thailandicum and Microsorum siamenseĪs their species names suggest, these two iridescent blue ferns are native not to Pandora, but to Thailand, where they are found growing among or on limestone rocks.
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