Fogbows are rare and captivating phenomena often described as ghostly or white rainbows. Unlike the colorful rainbows we usually see, fogbows appear as pale, almost ethereal arcs in the sky. But how is a fogbow formed? Let’s dive into the mysterious process behind this natural wonder.
How Is a Fogbow Formed?
A fogbow forms through a combination of light diffraction, reflection, and refraction, similar to a traditional rainbow, but with key differences due to the size of the water droplets involved:
- Tiny Water Droplets: The primary factor that differentiates a fogbow from a rainbow is the size of the water droplets. Fogbows form in fog, mist, or low clouds, where the water droplets are typically less than 0.05 millimeters in diameter. These droplets are much smaller than raindrops, which are essential for forming a standard rainbow.
- Diffraction of Light: As light passes through these tiny droplets, it bends (or diffracts) around them rather than being fully refracted and reflected as in a traditional rainbow. This diffraction spreads the light more evenly, which prevents the formation of distinct colors and results in a broad, white arc—the fogbow.
- Lack of Color: Because the droplets are so small, the different wavelengths of light do not spread out enough to create the full spectrum of colors. Instead, the light overlaps and the fogbow appears mostly white, with only the faintest hints of color at the edges
- Sun Position: Fogbows are typically seen when the sun is low in the sky, such as during early morning or late afternoon. The sunlight needs to be behind the observer, shining into the fog, to create the fogbow. This angle enhances the diffraction and makes the fogbow visible.
FAQ
How is a fogbow formed?
A fogbow is formed by the diffraction of sunlight through tiny water droplets in fog or mist, resulting in a pale, white arc instead of a colorful rainbow.
What makes a fogbow different from a rainbow?
Fogbows are formed by much smaller droplets than rainbows, causing the light to diffract more and spread out into a broad, white arc without distinct colors.
Why are fogbows white?
The small size of the droplets prevents the light from separating into the full spectrum of colors, resulting in a mostly white appearance.
Where are fogbows most likely to be seen?
Fogbows are most commonly seen in areas prone to fog, such as coastal regions, near large bodies of water, or in mountainous areas.
Can fogbows occur at night?
Yes, although rare, fogbows can also occur at night when illuminated by a full or nearly full moon, in which case they are known as “lunar fogbows.”
