During such good visibility conditions, the larger but fainter secondary rainbow is often visible. The result is a luminous rainbow that contrasts with the darkened background. The most spectacular rainbow displays happen when half the sky is still dark with raining clouds and the observer is at a spot with clear sky in the direction of the Sun. Because of this, rainbows are usually seen in the western sky during the morning and in the eastern sky during the early evening. Rainbows can be observed whenever there are water drops in the air and sunlight shining from behind the observer at a low altitude angle. Rainbows may form in the spray created by waves These include not only rain, but also mist, spray, and airborne dew. 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 may see a different rainbow-farther off-at the same angle as seen by the first observer, or even none at all. 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. Overview 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. Double rainbow and supernumerary rainbows on the inside of the primary arc.

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