Rainbows

Rainbows are among nature’s most beautiful optical illusions, appearing when sunlight interacts with water droplets in the atmosphere. They may look simple, but every rainbow hides fascinating physics, strange shapes, and colorful surprises.

• Sunlight Makes Rainbows – A rainbow forms when sunlight enters tiny water droplets, bends, reflects inside them, and exits again. This process separates white sunlight into its different colors.
• Seven Colors? – Rainbows are traditionally described as having seven colors: red, orange, yellow, green, blue, indigo, and violet. In reality, the colors blend continuously into one another rather than forming seven distinct bands.
• Rainbows Are Circles – A rainbow is actually part of a complete circle. From high enough above the ground, such as from an airplane, you can sometimes see much more of the circle.
• Red Sits Outside – In a primary rainbow, red appears on the outer edge while violet is on the inner edge. This happens because different wavelengths of light bend by slightly different amounts.
• A Rainbow Has No End – You cannot reach the “end” of a rainbow because its apparent position depends on where you are standing. Move toward it, and the rainbow appears to move too.
• Double Rainbows – A secondary rainbow can appear when light reflects twice inside water droplets instead of once. Its colors are reversed, with red on the inside and violet on the outside.
• Dark Between Them – The darker region between a primary and secondary rainbow is called Alexander’s band. It appears because fewer rays of refracted sunlight reach that part of the sky.
• Moonbows Exist – Rainbows can also be created by moonlight rather than sunlight. These rare “moonbows” are usually much fainter and can appear almost white to the human eye.
• No Two Are Identical – Every rainbow depends on the exact position of the Sun, water droplets, and observer. Change any of these, and you get a slightly different optical display.
• You Can Make One – You don't need a storm to create a rainbow. A garden hose or spray bottle can produce one when sunlight hits the tiny droplets at the right angle.