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"Roses are red, violets are blue…" but wait, what color is the violet in a rainbow? Have you ever looked closely and wondered why the blue seems a bit off, or noticed a hint of purple? Get ready to dive into the fascinating world of rainbows, where we'll uncover the truth about violet, the mystery of purple, and the magic of supernumerary bows!
You probably learned the rainbow's colors as ROYGBIV: Red, Orange, Yellow, Green, Blue, Indigo, and Violet. But did you know that Isaac Newton, the guy who first systematically studied rainbows, had a slightly different idea of blue? What he labeled as "blue" is closer to what we'd call cyan or teal today – that blue-green shade reminiscent of a clear sky. And the color we often call blue? That was Newton's violet! Think of the deep, rich blue of a violet flower.
So, where does indigo fit in? Well, some argue that Newton added it simply to match the seven notes of the musical scale. Interesting, right?
Now, let's talk about purple. You won't find true purple in a rainbow created by a prism because it's a combination of red and blue light, which are on opposite ends of the spectrum. But what about those times when you swear you see a hint of purple in a rainbow across the sky?
Sometimes, it's an optical illusion. Our eyes can be tricked into seeing purplish hues when deep blues are surrounded by lighter colors. But here's the truly fascinating part: sometimes, purple in a rainbow is real!
You see, a rainbow isn't just a simple arc of colors. It's actually a rain-disk, with each color of sunlight reflecting back in a bright-rimmed disc of a different size. These discs overlap, creating the white center and colorful rim we associate with rainbows.
But wait, there's more! Light behaves like a wave, and interference from those tiny raindrops creates multiple rings within each color disc. The bright outer ring is the one we usually see, but fainter, inner rings called "supernumerary rings" can appear, especially when the raindrops are small and uniform in size.
And guess what happens when the first red supernumerary ring overlaps with the main blue ring? You guessed it – purple! So, that touch of purple you sometimes see isn't just your imagination; it's a testament to the incredible physics at play in a rainbow.
So, the next time you're lucky enough to witness a rainbow, take a closer look. You might just spot those elusive supernumerary bows and the subtle hint of purple, reminding you that even the most familiar natural phenomena can hold hidden wonders.
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