Double Rainbow
Luca Saltarelli
Award: Top 100
School: saint xavier high school
Teacher: jennifer boughton
Category: Natural
Photo #20728
Double Rainbow
My photograph captures a vivid double rainbow formed just after a rainstorm, when sunlight interacts with countless suspended water droplets in the air. A rainbow appears due to three key processes: refraction, reflection, and dispersion of light. As sunlight enters each raindrop, it slows down and bends--a process known as refraction--because light travels at different speeds in air and water. Since white light is composed of many wavelengths, each color refracts at a slightly different angle, causing the light to spread into a spectrum.
Inside the droplet, the light reflects off the back surface before refracting again as it exits, directing the separated colors toward the observer. This process, repeated across millions of droplets, produces the bright primary rainbow seen in the image. The colors follow the familiar order from red on the outer edge to violet on the inner edge.
The secondary, fainter rainbow forms through a similar but more complex path. Light undergoes two internal reflections within each droplet instead of one before exiting. This additional reflection not only reduces the intensity of the light, making the second arc dimmer, but also reverses the order of the colors. As a result, the outer rainbow displays red on the inner edge and violet on the outer edge--opposite of the primary bow.
Together, these overlapping optical effects create the striking double rainbow captured in my photo, illustrating the precise and beautiful interaction between light and water in nature.
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