This phenomenon can be confused with the glory phenomenon, but a glory is usually much smaller, covering only 5–20°. The shadow of the photographer's head at the bottom of the photograph marks the centre of the rainbow circle (the antisolar point).įrom above the Earth such as in an aeroplane, it is sometimes possible to see a rainbow as a full circle. Double rainbow and supernumerary rainbows on the inside of the primary arc. Now that software for stitching several images into a panorama is available, images of the entire arc and even secondary arcs can be created fairly easily from a series of overlapping frames. For a 35 mm camera, a wide-angle lens with a focal length of 19 mm or less would be required. It is difficult to photograph the complete semicircle of a rainbow in one frame, as this would require an angle of view of 84°. As human visual perception for colour is poor in low light, moonbows are often perceived to be white. 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. It appears about 10° outside of the primary rainbow, with inverse order of colours. 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. 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. These include not only rain, but also mist, spray, and airborne dew. Rainbows can be caused by many forms of airborne water. 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. A rainbow is an optical phenomenon caused by refraction, internal reflection and dispersion of light in water droplets resulting in a continuous spectrum of light appearing in the sky.
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