Eli5: How does the colour purple “not exist”?
In: Physics
When people say purple “doesn’t exist” they are talking about pure, single-frequency light.
A single photon of light will have a specific wavelength. That wavelength will correspond to a colour. We can also have multiple photons with different wavelengths, and together they will look like a different colour.
[Take a look at this chart](https://cdn-dkepej.nitrocdn.com/xHPizjaXJNONuYnLnfsGSUCsMnIlzOEq/assets/images/optimized/rev-5c79e86/blog.frame.io/wp-content/uploads/2020/02/4a-2D-Plot-Rec-709.png). Every colour along the curved edge is a pure, single wavelength colour. Everything on the inside/along the straight line requires 2 or more “pure” colours to be mixed for you to see that colour. And as the chart shows purple is along the straight line, meaning it needs to be a mix of colours.
So purple doesn’t exist in the sense that there is no purple wavelength of light. But pretty much all colour is a mix of wavelengths, so defining “real” colour as “has a single wavelength of light” is not a useful definition.
Latest Answers