Question

What IS reflection?

Answer 1

Or, to be more precise, what happens on the atomic level?

Answer 2

what reflection at atomic level?

Answer 3

My question is what actually is reflection: all the laws about how to work out when things will reflect are fine, but in terms of absorption and emission (if this is the cause) in atoms, when light reflects, what is happening?

Answer 4

this is something i would like to figure out too ...

Answer 5

i believe you are referring to the case of waves ... EM waves

Answer 6

Or quantum mechanically, but I don't know how different the two answers would be

Answer 7

i.e. photon particle-waves

Answer 8

you mean ... a particle photon colliding with particle nucleons ?

Answer 9

Yes, I assume that in reflection this happens, or else the photons wouldn't turn around, but I doubt that it can be normal absorption/emission, as black things can "emit" white reflected light.

Answer 10

this is quite complicated ... understanding is impossible without Electrodynamics and Quantum mechanics. But the laws of reflection and transmission is classically when on different medium.

Answer 11

'understanding is impossible without Electrodynamics and Quantum mechanics': could you not try to half-explain?

Answer 12

I understand that EM waves are perpendicularly mutually inducing electric and magnetic field which also has momentum.
When waves enter a medium, they are entering on different electric and magnetic field ... there there will be some electromagnetic interaction.

Answer 13

I honestly don't understand Quantum mechanics at all ...

Answer 14

"If you think you understand Quantum Mechanics, you don't understand Quantum Mechanics"

Answer 15

i took QM for a year ... still having problems understanding CM

Answer 16

how about this...reflection might not be at the atomic level....but deals more with the combined product of the atoms...when light falls on the material..certain phenomenons might be occuring simultaneously..

Answer 17

I suppose so, but the fact is that- take (green) binbags for an example- binbags normally take white sunlight and emit green light, but when the angle is right it turns all of the sunlight around, and how could it do that without absrobtion/emission?

Answer 18

binbags??

Answer 19

http://en.wikipedia.org/wiki/Bin_bag
That's what Britons call them

Answer 20

how to you turn it around?

Answer 21

possibly there is a way in which every material absorbs the light energy that falls on it. it is the position of our eyes that does the trick..

Answer 22

That's what reflection essentially does, and my question is how that happens

Answer 23

let's try to understand what happens to sound ... when it get's reflected and refracted.

Answer 24

what i am trying to say is that..light will fall on all sides..but we see the phenomenon of reflection because of the particular angle of our eyes...if we had not known any better..the same thing might be happening on all sides..the absorption and emission of light i mean..

Answer 25

light is again an energy wave...so the absorption must be in the same way as we have learned in our schools

Answer 26

let's keep this discussion for future.

Answer 27

yup sure..

Answer 28

Actually, white light could be reflected if all electrons jumped back into exactly the same energy levels they were in before the light excited them...

Answer 29

true..but how does that concern your question here?

Answer 30

It may be the mechanism of (syncronised) reflection, although I haven't stated why it occurs

Answer 31

hmmm...this is complicated..

Answer 32

At the atomic level, the outer electrons absorb the photon & jump to a higher energy level. When these electrons jump back, they emit a photon of exactly the same energy as the one they absorbed. This is the photon that you see from the mirror.

Answer 33

For the explanation about green binbags, see attachments.

Answer 34

Thanks, but why does the shiny surface sometimes reflect wholly white light ( http://upload.wikimedia.org/wikipedia/commons/c/c8/Garbage_bag.jpg for instance)? Is it a transparent layer over the black or is it the black bit itself?

Answer 35

If you would spend some time, there are a very decent freshman level type of lectures that explain this... Immensely highly recommended...

http://vega.org.uk/video/subseries/8/

Answer 36

I've seen those lectures, and however brilliant an introduction to QED they are, Feynman covers more the rules for working out where light will reflect to and from without going into the actual mechanics of reflection

Answer 37

I assume you have read .
QED: a strange theory of light and matter.
It may not have much mathematics in it, but it is very good at illustrating the basic concept.

Answer 38

Is it any better than the video lectures from which it was adapted for covering this question, as in the video lectures Feynman didn't explain what was actually -really- going on in reflection, only assumed that it happened to explain his path-integration theory thingy?

Answer 39

I don't know, I haven't seen the lectures. Likely not, but it's a short read.