Why Do We Sometimes See Two Rainbows?
Very often, we can see two rainbows, one within the other. The inner rainbow is the brighter one and is called the “primary” bow. The outer rainbow is sometimes very faint and is called the “secondary” bow. In the primary rainbow the colors are arranged from violet, on the inner edge to red on the outer edge, but in the secondary rainbow the order of these colors is reversed, the red being inside and the violet on the outside.
Light from the sun enters the top of a drop of rain and is re fracted or bent. This light travels to the back of the raindrop and is reflected to the bottom. The light is again bent when it leaves the raindrop. It is this light which reaches the eye. Sunlight is made up of many colors. As it enters and leaves the drop each color undergoes a different amount of bending. Hence when the
light reaches the eye the colors have been spread and separated, and we see a rainbow.
Our next drawing shows how the secondary bow is formed by light which enters the bottom of the drop.
This light, is bent upwards when it enters the drop. It is then reflected twice. When it leaves the drop it is again bent. It is this ray, which reaches the eye. This light comes to the eye at an angle different from that of the light shown in our first drawing. Hence there are two images formed. One image is that of the primary bow and the other image is that of the secondary.
