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Anonymous Fri 06 Nov 18:56:00 2020 No.12311951 View Reply Original Report

Quoted By: >>12311981 >>12311983 >>12311985

Can someone explain reflection to me?
The atom is not a solid object but 99% empty space
The photon is as small as an electron which is 1% the mass of the atom

How does light get reflected back?
Does it have something to do with their wavelenghts oscillating in such a way that they cannot pass through the atom or something?

Help. I'm confused

Anonymous

Anonymous Fri 06 Nov 2020 19:03:47 No.12311981 Report

Quoted By:

>>12311951
lol here's 50 slides on scattering
http://www.tcm.phy.cam.ac.uk/~bds10/aqp/lec20-21_compressed.pdf

Anonymous

Anonymous Fri 06 Nov 2020 19:04:13 No.12311983 Report

Quoted By: >>12311992 >>12312661

>>12311951
The photon is really an electric field at right angles to a magnetic field.
The electric field is strong enough to get absorbed by the atom.
Because the atoms form a solid structure, the orbitals overlap and the wavefunction of the solid is a vast number of orbitals all at very close energy - a band.

So if a photon is absorbed by a solid insulator it will meet that band wavefunction and turn into vibrational and heat energy.

Now when there are metals, they have a free valence electron, so they can donate those electrons to the upper energy levels of the band where they can be freely excited by a photon. That is why metals are conductive, too. A small voltage easily excites a valence electron and allows a charge to flow.

So when a photon hits a metal, it won't be absorbed, it'll excite an electron in the band wavefunction and almost immediately be reflected. Because that wavefunction extends over the whole solid, it reflects the whole thing.

Anonymous

Anonymous Fri 06 Nov 2020 19:04:25 No.12311985 Report

Quoted By:

>>12311951
On those small scales, it's not balls hitting each other, it's instead (described by) ambient fields interacting - and it's not possibly not the best thing to think of a photon as a thing outliving the whole process and making a turn. It's another photon emission stemming from the interaction.
(Since I'm not a realist, I'll add the caveat and say that all the words I'm using above are those of the theory describing the physical phenomena - there "is" no photon or anything we have words for for that matter)

Anonymous

Anonymous Fri 06 Nov 2020 19:06:31 No.12311992 Report

Quoted By: >>12312017

>>12311983
And what about transparent stuff?

Anonymous

Anonymous Fri 06 Nov 2020 19:13:50 No.12312017 Report

Quoted By: >>12312069

>>12311992
Things that are transparent are insulators (no valence electron to excite, which would make them shiny) and have a small-scale crystalline structure (regular structure with few vibrational modes to excite), and no grain boundaries (which would scatter the photons). That means transmission is the main thing that happens. For example, silicon has valence electrons, so you can't see through it, but silicon dioxide, or glass, is transparent.

Anonymous

Anonymous Fri 06 Nov 2020 19:24:12 No.12312069 Report

Quoted By: >>12312091

>>12312017
Oh, yeah. Insulators also cannot reflect.
But what about transparent conductors

Anonymous

Anonymous Fri 06 Nov 2020 19:31:07 No.12312091 Report

Quoted By:

>>12312069
There aren't any truly transparent conductors for this reason. You can coat glass with a very thin layer of metal or doped semiconductor, but that's a surface only.

Anonymous

Anonymous Fri 06 Nov 2020 21:56:22 No.12312661 Report

Quoted By: >>12313378

>>12311983
Ok, but how does color work?
How can white light reflect only a certain color?

Anonymous

Anonymous Sat 07 Nov 2020 01:47:03 No.12313378 Report

Quoted By: >>12313765

>>12312661
The short answer is that electrons can only jump to certain energy levels and can only absorb or get excited by certain spectra of wavelengths of a photon.

I'm assuming that was a mistake and you didn't mean light reflecting light.

Anonymous

Anonymous Sat 07 Nov 2020 04:51:20 No.12313765 Report

Quoted By: >>12314437

>>12313378
No, I mean in a sense that color works by absorbing all visible wavelenghts while reflectling only a select few

How does it work?
What makes the electron in a wax crayon different from each other?

Anonymous

Anonymous Sat 07 Nov 2020 11:31:49 No.12314437 Report

Quoted By: >>12315673

>>12313765
>color works by absorbing all visible wavelenghts while reflectling only a select few
A photon is reflected when it doesn't have enough energy to raise the energy level of the atom or molecule lattice. There's a wide spectrum of wavelengths that can do that.

When the photon has enough energy to excite the lattice it gets absorbed causing electrons to jump to a higher energy state. Those electrons then move back to lower energy states by emitting photons of specific wavelengths in a random direction.

Anonymous

Anonymous Sat 07 Nov 2020 12:12:21 No.12314488 Report

Quoted By:

An atom isn't 99% empty space, it's 99% electron wave.

Anonymous

Anonymous Sat 07 Nov 2020 20:47:50 No.12315673 Report

Quoted By:

>>12314437
Is there any math that can quantify these like the Snells Law or something?

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