Question

What would light be like if there was no ability for light to make a rainbow?

Asked by: undisclosed sender

 Answer

Rainbow happens because the light coming from the Sun is 'polychromatic' - meaning: it is composed of many colors/frequencies. Once all colors of the spectrum combine together they generate 'white' light that we generally see. The moisture in the air (small water droplets, usually after the rain) acts as a color-separating medium and splits this white light into its composite colors and therefore you see a rainbow. If you want to imagine world without a rainbow then you should imagine that the light coming from the sun is 'monochromatic' meaning: single frequency - single color. Our world would be black and white i.e. dark and light, but there would be no visible colors, everything around us would be grayscale, and there would be no rainbow ... it would be a dull world!

Answered by: Anton Skorucak, M.S. Physics, PhysLink.com Creator


Monochromatic light is certainly ONE way to imagine a world without rainbows, but another that wouldn't sacrifice an otherwise colorful world would be to make light so that it would travel through water at the same speed, regardless of wavelength. It is the different speed of different wavelengths of light in a transparent medium that cause each color to refract (bend) differently. Because violet light travels through water more slowly than red, violet light bends the most and red light the least when entering a denser (slower) medium at an angle. If all visible wavelengths travelled through water at the same speed, no dispersion of colors would occur when they interacted with a spherical raindrop and there would, sadly, be no rainbows in the sky.

If you confined this magical behavior to water, you could still generate your own rainbows using prisms of glass, crystal, diamond, etc.

Answered by: Paul Walorski, B.A., Part-time Physics Instructor

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