A rainbow is merely a large band of parallel stripes, blended at the rims, which displays the full spectrum of colors that make up the sun's white light. This brilliant display appears to the naked eye when the sun's light breaks up as it passes through, the prism-like raindrops during a rain-shower. This immense, curved spectrum of light appears only when both the elements of sunshine and rainfall present. As the sunlight enters the falling raindrops, it breaks up into its true colors of red, orange, yellow, blue, and violet. These colors are always arranged according to their wavelengths, with red being at one end of the spectrum, and violet at the other. Once inside the droplet, the particles of colored light bounce from side to side, reflect off of the far side of the droplet, exit the droplet, and reassemble, according to their wavelengths, to form a rainbow. Simply because you happen to be in the right place at the right time, when both elements necessary to form a rainbow are present, does not mean that you will actually see one. For the human eye to see these multi-colored bands, ranging from red to violet, his body must be strategically positioned between the sun and the rain, with his back to the sun. If the sun, the eye, and the center of the rainbow's arc are not in a straight line, the show is over, before it began. This explains why we only see rainbows in the early morning or late afternoon…it is physically impossible for us to align our eyes with the sun at other times of day, as it is high above our heads! Logically, a morning rainbow appears when the sun shines in the east, and the rain falls in the west, and an afternoon rainbow appears when the sun shines in the west, and the rain falls in the east. parallel: 平行的 stripe: 条纹 spectrum: 光谱 prism-like: 象棱镜一样的   curved: 弯曲的   wavelength: 波长