Physics Question on Light and Colour

[TheHamster22]

Need some help finding some information out on light and colour if any of you physics folks on here want to lend a hand.

The question I pose to you is to find the answer to what exactly happens to light when it strikes an atom or molecule. I know its to do with electrons and they absorbed then reemit certain frequencies of light by jumping up and down energy levels, and that the frequencies of light absorbed all depend on molecular bonds, ambient conditions, spin, and what not.

However the nonabsorbed light is whats confusing me, what happens to the nonabsorbed light when it's passing through the atom, I know its reflected but why is it? It can't be striking anything because an atom is essentially empty space so I then become stumped as to what it making the light actually reflect the way it does. D: D:

Also if you find any snazzy science journals or any articles relating to this, that'll be a big +++

Ta very much halflife2.net

 

[Jintor]

If an atom is empty space, then wtf are you made up of?

 

[TheHamster22]

Mostly empty space, the diameter of a nucleus is about 1x10^-15 m and the atom in total is about 1x10^-10m so most of the atom by a long way is just nothingness. We're just mostly photons since thats whats interacting between the nucleus and electrons

 

[bbson john]

My conjecture is:
1. Photons are small, but there are many.
2. Photons are small, but the wavelenghts of the light wave aren't. Since we say "wave-particle duality", we must consider both particle and wave properties at once. In this case you've mentioned, the wave property grants light a great deal of license in being reflected. i.e. Wavelengths of visible light are far bigger than the gap between atoms. It is common that some phenomena in light are unexplained by, or even contradicted with, either light or particle theory. For instance, photoelectric effect cannot be explained by wave theory. Interference of light cannot be resolved by particle theory. That is all life about.

 

[Reginald]

A light photon hits an atom. The light energy is transferred into kinetic energy, making the electron "jump" to a higher ring. Sometimes this energy is high enough for the electron to break free from the parent atom, called ionization, making an atom pair. At this point, all the remaining atoms jump fall down to fill up the lower "levels" to "ground state" meaning the atom is stable once again.
If the electron doesn't "jump" out of the atom and merely to a higher energy level, it immediately falls back down to ground state and, the resulting energy of falling back down is released as a photon of light energy of a certain frequency.
The frequency can be calculated by an equation that escapes me at this moment in time.

That is roughly what happens. There is probably a more concrete definition than that, but that knowledge got me a solid B in my Physics A-Level Module 1. :bounce:

 

[TheHamster22]

nah I've got all that stuff, im more concerned with the light that isn't absorbed by the electron, and what thats doing. As it isn't all the light thats absorbed and then reemitted at a series of many different frequencies.

(and the equation is E=hf you baffoon! D: )

 

[NeptuneUK]

If an atom is empty space, then wtf are you made up of?

Mostly empty space. An atom is MOSTLY empty space.

 

[NeptuneUK]

edit: damn someone got here before me.

 

[TheHamster22]

I gave numbers to mwhaha

 

[bbson john]

Just in case... Did you read my wavelenght arguement?

 

[NeptuneUK]

What was the question again? Serously wtf are you on about? (not you, bbson john )

what happens to the nonabsorbed light when it's passing through the atom

It doesn't.

nah I've got all that stuff, im more concerned with the light that isn't absorbed by the electron

Then the light is not incident on the atom and is is not relavent to the question.





It's like asking what happens to someone in a car crash, but only if someone is not in the car. Best example I could think of.

 

[bbson john]

Basically, the light wave, not photon, hits atom and bounce back.

im more concerned with the light that isn't absorbed by the electron, and what thats doing. As it isn't all the light thats absorbed and then reemitted at a series of many different frequencies.

Then the light is not incident on the atom and is is not relavent to the question.

What if a light incident on a cluster of neutrons, or protons? Without electrons, it still does bounce back, I guess.

 

[Reginald]

What was the question again? Serously wtf are you on about? (not you, bbson john )



It doesn't.


Then the light is not incident on the atom and is is not relavent to the question.





It's like asking what happens to someone in a car crash, but only if someone is not in the car. Best example I could think of.

UK science > rest of the world :E

 

[TheHamster22]

Just to clean up my question abit >_<

What is causing a photon to bounce back off an atom, since its not actually hitting anything.

and bbson John I did read your bit on the waveparticle duality and I see your point, so essentially it could be just that the unasborbed light is being diffracted through the atoms, such that they end up coming back the direction they came? So the light passes through the gap of the first two atoms in a wall, diffracts, goes between two more, making it diffract again, etc until it comes back out the wall. Hmm is that what your getting at?

 

[Reginald]

Bounce back? That's a term I've not heard in relation to a photon. If it was perhaps a propelled electron you could talk about the positive charge of the nucleus of the atom repelling the electron back the way it came. But.. photon?

 

[ríomhaire]

 

[NeptuneUK]

Basically, the light wave, not photon, hits atom and bounce back.





What if a light incident on a cluster of neutrons, or protons? Without electrons, it still does bounce back, I guess.

Can you see protons?

 

[TheHamster22]

Bounce back? That's a term I've not heard in relation to a photon. If it was perhaps a propelled electron you could talk about the positive charge of the nucleus of the atom repelling the electron back the way it came. But.. photon?

Aye ok its not exactly the right terminology (at all). Though I'd imagine theres more going on, something quite massively unlike riomhaires diagram p).

I'm seeking to discover how the photons behave on an atomic level, but as bbson points out the wavelength of visual light is far to big to go within an atom, and is more likely to only be affected by adjancent atoms, through diffraction. Amirite?

Can you see protons?

Well in a round about way you can, using things like NMR on hydrogen atoms you can essentially see them.

 

[NeptuneUK]

A photon is just a packet of energy, if it 'collides' with something it is absorbed.
So..
If a photon hits a proton the proton gains energy.

 

[TheHamster22]

Ahha now we're getting somewhere. But that is just another part of the absorbtion spectrum, where the proton gains energy from the photon allowing it to change it spin to up (high energy) or down (low energy) and the change from high to low, will emit another frequency of light.

However not all the photons are absorbed in the atom, many wavelengths just pass right on through, but their courses are changed somehow. So what is happening to the none absorbed light, because something is, as its being reflected. Say like on a mirror, the light is reflected off and thats not the light thats reemitted by the electrons. As the electrons drop down from there higher energy states, to there ground states in any number of ways (incrementally or all in one go).

 

[Stigmata]

My conjecture is:
1. Photons are small, but there are many.
2. Photons are small, but the wavelenghts of the light wave aren't. Since we say "wave-particle duality", we must consider both particle and wave properties at once. In this case you've mentioned, the wave property grants light a great deal of license in being reflected. i.e. Wavelengths of visible light are far bigger than the gap between atoms. It is common that some phenomena in light are unexplained by, or even contradicted with, either light or particle theory. For instance, photoelectric effect cannot be explained by wave theory. Interference of light cannot be resolved by particle theory. That is all life about.

Having not read the thread past this post (stay with me now), I propose an awesome hypothesis:

What if photons are the medium through which lightwaves travel? A medium all but completely unaffected by gravity (again, stay with me) preventing the photons from collecting around planets and stars. So when we measure the motion of a photon, we're really measuring the propagation of a wave through the medium of photons?

It's flawless!

 

[99.vikram]

My explanation:-

When light hits an electron, some enrgy is absorbed, some is re-emitted. If it doesn't hit, nothing happens.

If photons hit protons, then it increases the energy of the protons. If I'm not wrong, protons have discreet energy levels as well.

 

[Stigmata]

*discrete

 

[AntiAnto]

I think this article might give you a highlight to your question.

http://www.ndt-ed.org/EducationResources/CommunityCollege/RadiationSafety/theory/interaction.htm

 

[99.vikram]

*discrete

Foiled again! Damn you meddling kids!! :flame:

 

[Dan]

My conjecture is:
1. Photons are small, but there are many.
2. Photons are small, but the wavelenghts of the light wave aren't. Since we say "wave-particle duality", we must consider both particle and wave properties at once. In this case you've mentioned, the wave property grants light a great deal of license in being reflected. i.e. Wavelengths of visible light are far bigger than the gap between atoms. It is common that some phenomena in light are unexplained by, or even contradicted with, either light or particle theory. For instance, photoelectric effect cannot be explained by wave theory. Interference of light cannot be resolved by particle theory. That is all life about.

Absorption is ewasy to explain. The wavelengths (colours) that get absorbed by an electron are only the specific wavelengths which possess exactly enough energy to excite the electron to the next valance orbit.

Reflection and Refraction I think cannot be explained by light behaving as a photon, you have to consider it as a wave. When light hits a slower medium, say light travelling through the air hitting the surface of water, it slows down. If you draw that out as a wave hitting a slower medium at an angle, one edge of the wavefront will slow down before the other edge does. This has the same effect as bending the wave as it passes through the boundary. Reflection is just well, reflection. The wave bounces off an optically dense medium.

http://theory.uwinnipeg.ca/physics/light/index.html
http://hyperphysics.phy-astr.gsu.edu/hbase/mod3.html#c1
http://elchem.kaist.ac.kr/vt/chem-ed/light/light-ma.htm
http://csep10.phys.utk.edu/astr162/lect/light/light-matter.html
http://www.wpi.edu/Academics/Depts/Chemistry/Courses/General/concept4.html

 

[theotherguy]

right. as people said before, the photon is not an actual particle but pure energy. Photons are "packets" of energy, so ones that are reflected don't exactley go anywhere, the entire wave simply moves as the particle absorbs exactley one photon.

At least, thats what I thought.

 

[TheHamster22]

Mmm thanks Dan and Antianto lots links there to digest ^_^

(A quick flick of them reveals that they do indeed look like they will hold the key to my question, woo!)

 

[Qonfused]

I hate the complexity that teachers apply to the colors. It's red. It doesn't bounce off other colors. It's ****ing red.

 

[bbson john]

Having not read the thread past this post (stay with me now), I propose an awesome hypothesis:

What if photons are the medium through which lightwaves travel? A medium all but completely unaffected by gravity (again, stay with me) preventing the photons from collecting around planets and stars. So when we measure the motion of a photon, we're really measuring the propagation of a wave through the medium of photons?

It's flawless!

How well if the medium is called... well, ether? O well...
I suppose you are joking.

Reflection and Refraction I think cannot be explained by light behaving as a photon, you have to consider it as a wave. When light hits a slower medium, say light travelling through the air hitting the surface of water, it slows down. If you draw that out as a wave hitting a slower medium at an angle, one edge of the wavefront will slow down before the other edge does. This has the same effect as bending the wave as it passes through the boundary. Reflection is just well, reflection. The wave bounces off an optically dense medium.

Ya, it's my point! Reflection, refraction, diffraction and interference are phenomena that can be explained only by wave theory. Particle(photon) theory fails to explain this bit. You cannot deal with interference with particle theory, than you cannot deal with reflection with the same theory. Wave-particle duality, don't forget the word wave.

 

[357]

Lolz... if the photon travels through the empty space inside the atom it doesn't give off any energy at all... it just travels through the void, I guess...

 

[bbson john]

Ether had been proven that it doesn't exist.

 

[mortiz]

Wtf? Were you my science teacher?

 

[Stigmata]

Ether had been proven that it doesn't exist.

Actually, it's only been proven that a luminiferous ether, if it exists, doesn't have anything analogous to a red-shift or doppler effect. It might still be there, it's just that the speed of light through the ether isn't affected by motion.

 

[Solaris]

Actually, it's only been proven that a luminiferous ether, if it exists, doesn't have anything analogous to a red-shift or doppler effect. It might still be there, it's just that the speed of light through the ether isn't affected by motion.

My understanding is that now that we've somewhat abandoned Newtonian physics for explaining such things, it is no longer necessary that ether must exist and as there is no evidence that it does either we assume it doesn't.