With Rain Drop or Graph selection, a click inside the drop toggles between primary and secondary rainbows

If the sun is at an appropriate position when it is raining, you are in for a treat. If you stand with your back to the sun, you will be in a position to see a rainbow, if conditions are otherwise favourable. The rainbow forms a circular arc around the anti-solar point which lies on the dotted line (shown in the picture above).
It is possible to see the entire circle of the rainbow from an airplane since there are falling droplets both above and below you and the anti-solar point will be high above the ground.
A rainbow is a virtual image formed by many rain drops, some closer and some far away. It is a pattern of light refracted by raindrops. The dispersed light from the drops reaching your eyes comes the from the raindrops located at the correct angle in front and above you. As the drops fall, each correctly postioned drop relative to the sun and your eye gets replaced by another.
You can "make" a rainbow with a hose pipe spraying water in to the air. You need to have your back to the sun and aim the hose at the correct angle for sunlight to be refracted and dispersed in to your eyes.

If your are way above the ground, like a pilot!

With Rain Drop or Graph selection:
Click/tap inside the drop toggles between primary and secondary rainbows

With the Rainbow selection:
Drag/swipe to change the orientation of the rain bow. Scroll to zoom in/out.
Notice the reversal of order colors of primary and secondary rainbows.

Illustration shows the passage of light through a rain drop.

Of the several rays incident on the drop we are interested in the behavior of the rays that produce the primary rainbow and the secondary rainbow.

Partial reflections and refractions occur at every point where the ray is incident but only relevant reflections and refractions are shown.

Primary rainbow is due to the rays incident on the top portion of the drop and secondary rainbow is due to the rays incident on the bottom portion of the drop.

The primary rainbow would be between angles of 40° and 42° to the horizontal and secondary rainbow between angles 51° and 53° to the horizontal. These are the rays that suffer minimum deviation as they are reflected and refracted and hence are brightest.

In the graph option observe the way the deviation is measured.

Observe the order of colors in the primary and secondary rainbows.