Yes, pink rainbows, often referred to as red rainbows, are indeed rare.
While all rainbows form due to the refraction and reflection of sunlight through water droplets, a pink or reddish rainbow occurs under specific atmospheric conditions that are less common than those that produce a typical rainbow.
Here's why pink rainbows are rare:
- Sun Angle: Pink rainbows are most likely to occur near sunrise or sunset. At these times, the sun is lower in the sky, and its light has to travel through more of the atmosphere.
- Scattering of Light: As sunlight passes through the atmosphere, shorter wavelengths of light (blue and green) are scattered away more easily. This leaves mostly the longer wavelengths (red and orange) to reach the water droplets.
- Water Droplet Size: Smaller water droplets also contribute to the effect. Larger droplets produce the typical bright, full-spectrum rainbow. Smaller droplets enhance the scattering effect, further diminishing the blue and green light and intensifying the red hues.
In essence, a pink rainbow is the result of a standard rainbow formation combined with increased scattering of blue and green light due to the sun's low angle and potentially smaller water droplets. Because these conditions don't always align perfectly, seeing a pink rainbow is a relatively uncommon and visually striking phenomenon.
