Why are rainbows arched?
Rays of a rainbow bend twice. As they enter the drops, the rays are light bent, then reflect off the back of the drops and bend again as they exit the drops. Each drop reflects only one color of light so you can imagine how many drops there must be when you get colors of gold/violet/pink, etc. The rainbow is circular because when a raindrop bends light, the light exits the raindrop at a 40-42 degree angle away from the angle it entered the raindrop. The violets and blues bend at a 40 degree angle, and the oranges and reds bend at a 42 degree angle. Rainbows don’t have “ends” but are full circled, but we can’t see this because the horizon of the earth is in the way. If the sun is very low in the sky, either just before sunset or just after sunrise, we can see a half circle. The higher the sun is in the sky, the less we see the rainbow.
