Question

on the same time we can observe two rainbows wherever. Why?​

Answer 1

Explanation:

Since they can only exist at a particular angle (with respect to you and the Sun), you can never see them anywhere else in the sky. All rainbows form a circle 84° across and exactly opposite from the Sun, no matter where you are. ... This comes about because of how rainbows are created.

Answer 2

Answer:

Physicist: A rainbow is an angle-dependent illusion. They don’t actually exist anywhere, they just appear to. Since they can only exist at a particular angle (with respect to you and the Sun), you can never see them anywhere else in the sky.

The next time you see a rainbow, draw an imaginary line from the sun through you. You’ll notice that this line goes exactly through the middle of the rainbow. This comes about because of how rainbows are created. No matter where you are, the red line is 138 degrees from the sun and the purple line is 140 degrees from the Sun.

For very small drops of water the surface tension overwhelms all other forces, and the drop is pulled into a nearly perfect sphere (which has nice optical properties). When light encounters the surface of water (or anything at all really) it splits into its component colors. As the light travels into the drop the various colors mostly end up getting scrambled so much that almost anywhere you look you’ll see a more or less even combination of them (white light). However, light that enters the drop, reflects off the back, and leaves again at about 42° from the direction it came from produces colors that stay separated.