how does light determine something’s color and why are things different colors?

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I teach art and am starting a unit in color, I’d really like some easy explanations to share with my middle schoolers

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2 Answers

Anonymous 0 Comments

“Color” is just how our brain interprets different frequencies of light. E.g. if some light with a wavelength of 650 nm enters your eye, your brain tells you that’s red.

The color of a thing in the world is basically down to which wavelengths it reflects and which ones it absorbs. If an object reflects a lot of red light and absorbs most other colors, we see that thing as red. If an object reflects all colors a lot, we see that as white (which is basically all of the wavelengths in roughly equal amounts). If an object doesn’t reflect very much light at all, we see it as dark or black.

Anonymous 0 Comments

Our eyes have things in them called “rods” and “cones”. These can detect different frequencies of light waves (really only the fundamental colors). Our brain combines these inputs to give us the sensation of color depending up on which ones are stimulated and how much for any given patch.

Light waves can be generated in different frequencies (such as when particles are stimulated). These move around, sometimes passing through things (or rather, exciting things to generate waves at the same frequency) or being absorbed. Some things can only pass on certain frequencies and other things absorb only certain frequencies.

For instance, grass is green because it has particles which absorb everything but green frequency, which it passes on. If some incoming green frequency light is bounced off, then our eyes see the green frequency. If you only sent red frequency light onto grass, all of that would be absorbed, so it would look black.

Green lights, however, could be generated by exciting certain substances which generate light waves in the green only frequency, or it could be white light which passes through a filter which absorbs everything but green.