Sunlight and showers for rainbows

Press, 6 November 1984, Page 11

Sunlight and showers for rainbows

The changeable spring weather we are now having can produce conditions ideal for rainbows. A rainbow is formed only when there is sunlight and showers at the same time. To see a rainbow, the sun must be behind you and the rain in front — as the sun shines over your shoulder, the raindrops break up the light into a spectrum or band of colours. Sunlight, or ordinary white light, is a.mixture of all colours. These colours can be separated through a prism; in the case of a rainbow the raindrops act as prisms. The colours are bent at different angles, red having the least angle followed by orange, yellow, green, blue, indigo and violet. This is the order of colours in a rainbow, with red on the outside edge and violet on the inside.

Sometimes a second and fainter rainbow is seen outside the first. This outer

bow has the colours reversed, with the red inside and the violet outside. It is caused by the beams of light being reflected twice inside each raindrop. The lower the sun is in the sky, the bigger the rainbow. When the sun rises in the sky it is not possible to see a rainbow, because of the angle of the light rays. Consequently rainbows are most often seen in the early morning or late afternoon. The discovery of how rainbows were formed was not made until about 1600. Before that the appearance of a rainbow aroused wonder and awe in many people, and rainbows were the subject of many legends and superstitions. A commonly-held belief was that if you could get to the end of the rainbow there would be a pot of gold. Some people believed that souls went to heaven on the bridge of a rainbow, and when one appeared it meant someone was going to die.