Answer to Question #26596 in Optics for Emmanuel Mafwenga
If light travels in a straight line, why a rainbow appears curved?
A rainbow is an optical and meteorological phenomenon that is caused by reflection of light in water droplets in the Earth’s atmosphere, resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun. Thus, a rainbow is not an object, and cannot be physically approached. Indeed, it is impossible for an observer to manoeuvre to see any rainbow from water droplets at any angle other than the customary one of 42 degrees from the direction opposite the Sun. 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 further off - yet, at the same angle as seen by the first observer. A rainbow spans a continuous spectrum of colours. 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