Rainbows occur when sunlight is refracted and then reflected by raindrops. The raindrops act like a prism, breaking the light into the colours of a rainbow, with red on the outer, and blue on the inner edge. On occasion the light can be reflected from both the front and back of the raindrops and two rainbows are visible, with the colour bands in the second opposite to those in the primary rainbow. Rainbows can be seen when the sun is shining and the air contains water spray or raindrops. This condition occurs frequently during or immediately following showers. Rainbows are always observed in the portion of the sky opposite the sun. The sun, the observer's eye, and the centre of the rainbow arc always fall on a straight line.