How do dyes work in regards to the light being reflected?

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So am apple is red because it absorbs all other colours/light on the spectrum and reflects the red back to your eye. Same with anything of any colour as far as I’ve seen.

So how do dyes work when you change them from one colour to another? What are you altering in the fabric that allows it to now absorb the colour it was and reflect a different colour?

In the same vein, what is bleach doing when it removes colour?

In: Physics

2 Answers

Anonymous 0 Comments

A lot of this relates to chemical structure. Basically, molecules can absorb energy from light at specific wavelengths, depending on said structure. We largely do not see this, unless the wavelengths they absorb are in the visible spectrum. — Relatedly, UV is dangerous because it is high energy *and* absorbed by very important DNA molecules in the body, causing damage. This absorption profile just depends on the molecule, and may be somewhat unique, but follow trends based on arrangement / electron arrangement / surrounding chemical environment / etc.

Changing dye colors usually means altering their chemical structure, or introducing them to something that changed their chemical context, thus changing the wavelengths they absorb/miss.

Bleach is a strong chemical, to my knowledge usually a strong oxidizer or base, so it’ll provoke a good deal of chemical change–either by directly disrupting the coloring molecule or by disrupting bonds and allowing it to be removed. After all, bases are essentially the complement to acids, and can be just as destructive.

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