Why can I see the complete rainbow?

The full circular rainbow is mainly formed by the internal reflection of raindrops on sunlight, which is related to the photographer's position.

Once in Australia, a photographer photographed a whole circle of rainbows on a helicopter. The whole rainbow phenomenon has a great relationship with the observer's position, which is mainly caused by the internal reflection of raindrops on sunlight. It is said that the full-circle rainbow is actually not a spectacle, just because on the ground, observation is limited, so you can't see the complete full-circle rainbow.

The rainbow is formed because the sun shines on the small round water droplets in the air, causing dispersion and reflection. When sunlight enters a water drop, it will be incident at different angles and reflected at different angles in the water drop. The appearance of rainbow is not a specific position in mid-air, but an optical phenomenon seen by the observer, and the position of rainbow will change according to the position of the observer.

When the observer sees the rainbow, its position is opposite to the direction of the sun, and the central position inside the rainbow arch is reflected by water droplets, which magnifies the image of the sun. So the sky inside the rainbow looks brighter than the sky outside the rainbow. The center of the rainbow arch is generally the direction of the observer's head shadow, and the rainbow itself is 40 to 42 degrees above the straight line between the observer's head shadow and his eyes. When the sun is higher than 42 in the sky, the position of the rainbow is invisible below the horizon, so the rainbow rarely appears at noon.

In England, someone photographed a whole rainbow. It is very rare to see the whole rainbow, and you need to have the right time and place. So only pilots or skydiving enthusiasts can see it. There is scientific evidence that all rainbows are round, but they are invisible on the ground. So the reason for the formation of a full circular rainbow is the same as what we usually see.