How A Rainbow Can Form Without Rain 😲

Rainbow is an optical phenomenon which is generally associated with rain, mist, and even fog. Some or the other form of water is thought to be required in order for a rainbow to form. But have you ever noticed a rainbow formation in a specific spot, like near a window at home? The conditions have to be just right, which makes it a cool little surprise when it happens!

Now, the sunlight keeps hitting the glass window all through the day so why is it that rainbow is only a rare occurrence? Dispersion or splitting of white light is a simple physical formation and yet rare to sight in day to day life. That is why, every time you spot a rainbow out of nowhere, it evokes a sense of joy and wonder isn't it?

For the rainbow effect to pop out, the light has to strike the glass window near a "critical" angle. The sun moves in the sky and it is only a specific moment in time when the angle of incidence is accurate enough for rainbow to appear. It is not a full arc like a sky rainbow because the geometry of a window pane is not the same as the spherical shape of a raindrop, but the physics is identical: refraction, dispersion, and a bit of reflection.

Why light splits into colors?

White light, or sunlight which is made up of all visible wavelengths, doesn’t bend uniformly, as each color, having different wavelength bends differently at a slightly different angle. As a general rule, shorter wavelengths, like blue, bend or refract more than longer ones like red.

Some cool facts about rainbow

1. No two people see the exact same rainbow since a rainbow is formed by light refracting through specific raindrops relative to your position. The exact rainbow you see depends on where you’re standing. Move a little, and it’s a different set of raindrops creating the effect.

2. The order of colors is always the same—red, orange, yellow, green, blue, indigo, violet, because of how light bends at different wavelengths.

3. A rainbow formed by light of the Moon, is called moonbow. The amount of light available even from the brightest full moon is far less than that produced by the sun so moonbows are incredibly faint and very rarely seen.