Eli5: Why do things have the colors they have? I know that colors are just different wave lenghts, but why does an egg yolk for example reflect the waves that make it yellow? Why isnt it for example reflecting green waves? I dont understand how things “decide” what kind of light they reflect.
In: 8
Things are made of atoms. Atoms have little electrons zipping around. These electrons can be farther or closer to the core. The more energy they have, the farther away they tend to be. If you add energy (like shining a light or adding heat for example) they will jump farther away from the core. It can’t stay up there forever, so it will release some of its energy to drop back down. Sometimes the energy comes off as light. Different atoms and molecules will give off different amounts of energy between these jumps, making different colors. It is just a weird quirk of what the thing is made of, not so much of a decision. There isn’t a good reason for the yolk of the egg to be yellow, it is just that the stuff it’s made of just so happens to give off yellow wavelengths of energy
Oh boy, this is a question about quantum mechanics.
So imagine you’re jumping rope. You can spin the rope slowly and complete one revolution per jump, or speed it up and go around twice per jump.
You can’t go around 1.5 times per jump, since you’re just gonna collapse the wave.
Materials are bound by the same concept when they interact with light. They can absorb and emit at the specific frequencies that correspond to “jumps” in their vibrational and electronic energy levels. Anything else is no-man’s-land that bounces off.
What those frequencies are vary based on the size and shape and characteristics of the molecule, so every material is different.
The simplest answer is: The materials are just better at absorbing some wavelengths and reflecting others. For a simplified, layman’s way of thinking about it, it’s not too much different than how a filter with different sized holes can let some particles through and not others.
In reality though it’s quantum mechanics and complicated material science. Sometimes it is like a filter, with certain wavelengths fitting through and some not, sometimes it’s electron shells absorbing and re-emitting light, and a whole bunch of other weird reasons that also change depending on if you’re talking about dielectric vs. non-dielectric materials. Cool stuff if you’re into it (I used to work as a 3D graphics programmer and did a fair amount of work in physically based light transport and loved learning about it), but far beyond ELI5.
Latest Answers