Optical illusion

Rainbows are spectacular optical illusions! For Rene Descartes’ description of a rainbow in 1637, click here.


Rainbow: light passing through water drops from Planet Pals


Here are some Q & A highlights about rainbows from Weather Wiz Kids:

How do we get rainbows?
Rainbows are spectacular rays of color. Sunlight looks white, but it’s really made up of different colors…red, orange, yellow, green, blue, indigo, and violet. The sun makes rainbows when white sunlight passes through rain drops. The raindrops act like tiny prisms. They bend the different colors in white light, so the light spreads out into a band of colors that can be reflected back to you as a rainbow.


Where do you look for a rainbow?
Three conditions must be met in order for you to see a rainbow. First, it must be raining. Second, the sun must be shining. Third, the observer must be between the sun and the rain. The lower the sun is in the sky, the higher the arc of the rainbow will be.


Can rainbows make a full-circle?
If you could get up high enough in the sky, then you’d see that some rainbows continue below the horizon. That’s because when the sun and rain combine to make a rainbow, they really make a full-circle rainbow. We can’t see all of the circle, because the horizon blocks it from our view. Pilots high in the sky do sometimes report seeing genuine full-circle rainbows.

Are there double rainbows?
Yes, they do happen! The inner and brighter rainbow has the red on the top and the blue on the bottom side. The outer and dimmer rainbow has the color scheme reversed.
Double Rainbow

What is an upside-down rainbow?
An upside-down rainbow is an unusual phenomenon caused by sunlight shining through a thin, visible screen of tiny ice crystals high in the sky. Interestingly enough, it has nothing to do with rain. Some people refer to this as a ‘smile rainbow’.

Upside-down Rainbow

Why can’t you ever find the end of a rainbow?
A rainbow is an optical illusion, so you just can’t catch up to it. When you move, so does it!

Can a rainbow appear during the night?
Yes, they’re called moonbows! The nighttime rainbow is very rare and occurs only when the moon is bright enough and positioned properly with respect to falling rain to produce the beautiful effect.
Lunar Rainbow

Powers of 10 project:  Create your own optical illusion – click here for activities at Weather Wiz Kids!

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