[Zer0 (OP)]

When a Black Surface is placed under Sunlight, it gets Warmed Up.

How?

P.S. - Try explaining it like you would to a 5 year old.
(Tankz!)

[Eternal Student]

Hi.

"In simple terms"   is what you asked for.

We (human beings) convince young children that Energy is a "thing",  and use the word "energy" in phrases much the same way as if it was something like orange juice.  Orange juice is a "thing" and a lump of stone is a "thing".   We learn there are things and Energy is treated as a thing.
   So the children assume it's some kind of thing.   As the children get older they start to sort out that some things are less like a physical thing than others.

Mum:  Get some sleep !
Child:   OK... is it in the cupboard?

  Children learn that sleep is not a thing like orange juice is a thing.  Orange juice is most definitely a physical thing but sleep is hardly worth putting in the same category,  it's a weird thing if it's thing at all.

   When you get to school people will still consider Energy as a thing.   However, when you study some science it should start to occur to you that Energy is one of those weird things,    a psuedo-thing at best.    It's not any sort of ordinary physical thing.   You can't point to it.   You can't find it in the cupboard.   However, people say that there is energy  "in"  some physical things.   

Mum:  Eat your potatoes, there's plenty of energy in those
Child:   Where?  When you cut it into little pieces all you find is potato all the way through.

   Anyway....  this is taking too long so we'll fast forward a bit....

We (human beings) have made our own problems by convincing ourselves (and misleading our children) to imagine that energy was a "thing" in the first place.
   It is certainly not any ordinary sort of physical thing.   In all of the particle physics experiments that have ever been done,  we have never found a particle of energy.    It's not there... a potato really is just potato all the way through, no matter how finely you dice it up, you can't find the energy that was supposed to be in it.


So what is Energy?
   It's any one of these,  take your pick:

1.   An oversimplified concept where it is imagined to be a "thing" that exists in the universe but distributed or spread out in some very specific ways.  So that there can be stores of it at certain places and/or it can be contained within certain physical objects.

2.    A quantity,  just some number which we might call E.   It just turns out that many physical systems have a quantity which is conserved  (doesn't change with time,   or is the same value at the beginning and at the end  etc.).    These conserved quantities aren't always called "Energy",   sometimes there's a conserved quantity called  "angular momentum"  or   "proton number"   or   something else..... there are many conserved quantities,  they're not all the same in every system and they're not all conserved in every system.   However a quantity  E  that behaves like we would expect Energy to behave is almost always there in every physical system.   Furthermore, when we combine two systems we have studied so as to construct one new but larger system, then we can usually feed the conserved quantity  E₁    from the first system  into the conserved quantity  E₂  of the second system and it works quite well.   Whenever there is some process to transfer some E₁  out of what was sub-system 1  and into   sub-system 2,  then we do see an appropriate corresponding  1 point for 1 point  increase in E₂.   That is, we do usually end up with a new quantity  E₃  =  E₁  +  E₂   which is conserved.    This gives us good reason to believe that E₁   from subsystem 1 really was the same kind of thing as  E₂  in subsystem 2,   i.e.  that they were both forms of Energy.

3.   An approximation or simplification only.   Something that usually applies but not always.  There does seem to be some systems where what we thought was Energy and should be conserved is  NOT  actually conserved.      Example:    The passage of light through an expanding universe where the frequency of the light would decrease over time.


    ----   This is already too long so I'm going to end here.    I'll leave someone else to go through the specific example you mentioned.   They might explain it by tacitly assuming that energy is a thing but that is up to them.   ----

It is important to realize that in physics today, we have no knowledge of what energy is. We do not have a picture that energy comes in little blobs of a definite amount. It is not that way.

     Taken from:   Feynmann lecture #4    "Conservation of Energy".    Available at this URL:
https://www.feynmanlectures.caltech.edu/I_04.html
   
   This is one of the best introductions to the difficulties of understanding what energy could be (in my opinion).   Just bear in mind it's old and we've had a few more revelations about Energy since this.


Best Wishes.

[alancalverd]

In simple terms, there isn't a simple explanation or even a simple definition.  Energy is one of the quantities that is conserved in classical physics, and very few adults have any idea what that means.

You can introduce the subject to a child by looking at mechanical energy. Winding clockwork, drawing a bow,  or lifting a weight  with a rope and pulley involves the sensation of work, and then you can use the spring, bow or weight to do something "useful", so you must have put something into the system, which it then releases.That "something" is called energy.

[Zer0 (OP)]

Mum:  Get some sleep !
Child:   OK... is it in the cupboard?

lol @ Eternal

I remember from School that Energy is the Input for performing a Task.
Measured in Joules.

Well, from above replies I've gained alot more insight.
Seems like i ended up Biting alot more than i can Chew.

In Essence the OP is Resolved.
Good Job Folks!

P.S. - But what about the second part of the OP?
The Black Surface & Sunlight?
How does that Work?

[paul cotter]

Photons arriving from the sun carry this inscrutable "energy" according to E=hf, where f is the frequency and h is planck's constant. These photons are absorbed by the black surface, with minimal reflectance, and give up their "energy" to the surface and thus raise the temperature. On the original question we could also say that energy is the resultant from the decomposition of matter, according to E=mc²

[alancalverd]

Paul's 5-year-olds have clearly benefitted from an exceptional nursery education. Never mind the sand box, children, today we will be entertained by Max and Albert, and you can take home the A level physics paper to show your mummies and daddies. Remember to bring your university tuition fees next week: the best spectrophotometer made from a cornflake packet and a toilet roll wins a scholarship to Trinity!

We mere mortals have to resort to James Joule. We covered "work" yesterday by putting manual effort into lifting and pulling, and showed that it can be turned into kinetic energy. So now we are going to convert work into heat by rubbing two sticks together, then use the bicycle dynamo and lamp to convert work into light.

It's pretty obvious to anyone except Aristotle (never trust a philosopher, children - politicians offer you sweeties but philosophers will harm you for nothing) that light travels from a source to a receptor, and since we put work/energy into making light, light must be another form of energy.

Now what can we do with light? We can reflect it (with a white surface) or absorb it (with a black surface). So what happens to the energy if we absorb it? In the case of the black surface, most of it turns into heat.

[vhfpmr]

So the children assume it's some kind of thing.   As the children get older they start to sort out that some things are less like a physical thing than others.

Mum:  Get some sleep !
Child:   OK... is it in the cupboard?

When I hear phrases like "How many calories in that chocolate?" I sometimes think that most adults must think that a calorie is an ingredient, not a unit of measurement.

"How many inches in that string?"

[alancalverd]

"How many inches in that string?"

I've mentioned it before, but worth repeating here.
Back in the mists of prehistory I attended the welcoming speech by the Director of the UK National Physical Laboratory to new recruits. He opened thus:
"How long is a piece of string?  In law, it is exactly as long as I say it is. Your job is to tell me what to say."

[Zer0 (OP)]

Indeed Very Nicely Explained Mr Cotter

lol @ vhfpmr
(hope u don't mind me asking what does ur nickname mean?)

Now to get back to the Question...
Not so quick folks, hold on hold on..

I read another OP by Talanum1 @ New Theories.
The user was proposing their hypothesis of the phenomenon.

Was Refuted by views stating that an Electron does Not absorb a Photon.

I didn't Understand, hence Googled & came up with the Law of Conservation of Momentum.

It states if the Electron absorbs the Photon, then with transfer of Energy, even Momentum would be transferred.
That would project the Electron at the Speed of Light.
Hence, Not Possible.

Another view in that OP stated that Electrons just Scatter Photons.
So then how do Photons end up wiggling & jiggling Atoms to vibrate more to raise Heat/Temperature?

Or am i missing the point Completely?
Does Wave Particle Duality needs to be invoked in order to Understand the said Phenomenon?

P.S. - i don't wish to goggle the answer, so could someone please explain, Thanks!

[alancalverd]

It states if the Electron absorbs the Photon, then with transfer of Energy, even Momentum would be transferred.
That would project the Electron at the Speed of Light.

No.
https://byjus.com/physics/photon-momentum/ shows you how to calculate the momentum of a photon = h/λ.
If it is all transferred to an electron, you can calculate the subsequent velocity of the electron, knowing its rest mass. It's a lot less than c!

[Bored chemist]

Was Refuted by views stating that an Electron does Not absorb a Photon.

And electron on its own doesn't (usually)  absorb a photon.
And electron in an atom or molecule can.

[alancalverd]

Just a reminder to all correspondents:

P.S. - Try explaining it like you would to a 5 year old.

[Eternal Student]

Hi.

@Zer0    your confusion is perfectly understandable.    It's not obvious what is happening.

@alancalverd  gave a reasonable response but it might help to phrase it differently.
   A photon carries a certain amount of momentum.   It is a tiny amount.
     The electron would gain that momentum but this does not mean that it gains all the speed  of the incoming photon,  only the momentum that it carried.      There is a significant difference between speed and momentum.  You can find this explained in more detail in various places.     See, for example,   https://www.bbc.co.uk/bitesize/guides/zc9bv9q/revision/1   which is a website designed for  GCSE Physics  (students aged about 15,  which I know is a bit above the 5 year old range originally asked for).   A more simplified view would just consider how difficult it is to get a small object to a certain speed compared to a massive object.   You can change the speed of a toy car easily just by flicking it with your finger but flicking a full sized car with your finger won't change it's speed much.  Mass is important when considering how much momentum a thing has.

       The key point is that the electron is massive, so the electron doesn't need to change its speed very much in order to accommodate that tiny bit of extra momentum gained from the photon.
- - - - - - - -

   The next part of your question is a little more difficult to answer and does show that you have considered the situation quite a lot.    Temperature is usually considered as a measure of the vibrational energy of particles in a solid and it is not obvious why exciting an electron in one atom of that solid should make a whole set of atoms vibrate a bit more.

So then how do Photons end up wiggling & jiggling Atoms to vibrate more to raise Heat/Temperature?

I don't know, here's my take on it and how I might exlain it to a child (especially if I was having trouble getting them to sleep).

Answer strategy 1:     It just does happen.   We don't need to worry about the "how".    This is the approach that the subject of thermodynamics might take.   The internal energy of a solid  (the black surface you put under the sun)  includes all sorts of different forms of energy.   Some of that is vibrational energy of the atoms,  some of it is the energy of the electrons in orbits around the atoms.   Internal energy of various kinds can contribute to the temperature of the solid.   We don't worry about how energy might be passed from one type of internal energy store to another.  All we notice is that this does happen, although it might take a little time.   Technically, temperature is only well defined and measured when some equilibrium has been reached.   This is just a way of saying that we shouldn't really measure temperature until some time has passed and the internal energy has distributed itself over all possible forms or modes of supporting internal energy that it can.   In practice the time we have to wait is very short, a thermal equilibrium situation can be reached in microseconds quite often.    Just to summarize,  a short answer is that we don't care "how", it just does happen that an excited electron can raise the vibrational energy of a whole set of atoms and thus raise the temperature of the solid.   This is a good answer not something to be dismissed.  It's good enough for thermodynamics which is a pillar of modern science and technology.

Answer strategy 2:    We can actually find some explanations if we try hard.  They will usually be specific to the type of substance that was receiving the photon.   We're going to stay very generic in this section:  The distance between the atoms will depend on things like electrostatic attraction between them.   If an electron in one atom gains energy then it is moved to a higher energy orbit, i.e.  in simple terms we can imagine it is moved further out from the nucleus.   This could directly affect their position a little by all sorts of mechanisms.   For example it could increase the amount of what is called "screening" that occurs between the two positively charged nuclei etc.   We start to get some movement, the beginning of our "jiggle" in the atoms.   In more extreme cases, the electrons may be moved to an orbit where chemical bonds can no longer be sustained and then there is a more significant movement of the atoms.  Many of these changes are temporary and short lived, so it's not as if you'll notice any chemical changes happening on a macroscopic scale.   These transient changes are just fine - we just want a little "jiggle" in the atoms.
   If you really were explaining to a child then explaining screening and chemical bonds will take a while.   You might just say the electron is charged and attracts or repels other atoms differently when you move it closer or further away.  So changing the orbit of an electron matters, it affects the pull between atoms and the overall distance you will get between atoms.
   
    In some cases it's as simple as realising that after a photon has been absorbed and adjusted an electrons orbit, the electron orbit doesn't stay in the excited state for very long.  It can just decay again with another photon being released.   For a while then,  the first atom (the atom as a whole) had to have some extra momentum (recall that it has just absorbed a photon), so it moved differently for a short while.  This might take a while to think about but the idea is that you can't just change the linear momentum (i.e. the motion) of an electron and expect it to stay with the nucleus it is orbiting around.  The electron would start to drift away - but that can't happen.  The electron and nucleus interact through electrostatic forces, pull on each other and try to hang together, if the electron had a change in its linear motion then the whole atom would.    Anyway, the next atom to briefly absorb the photon will have the same sort of brief disturbance of motion  etc.    The photons can be released in a random direction and could be fired out in the same direction from which they came in.  This means that atoms can pass momentum between themselves that can be double the momentum of the photon you find between atoms.   Now I have also said  "the" photon but there is no reason why a photon of the same energy has to be released as the one that was absorbed (the electron could decay into a middle energy state, if there is one, rather than falling all the way back down to the initial state it was in) - so with the random discharge direction as well, there is now quite a bit of random variation we can get in the momentum passed between atoms.
       Anyway.... we can build excuses and explanations to see how it might happen.   This is the sort of thing that would be done in the subject of statistical mechanics rather than thermodynamics.   It can be done.  Make it clear that these are partial explanations, excuses or "plausibility arguments".
       For a child, we walk away here and leave them to ponder that.   Since there may be others reading and considering what is the best approach to take when explaining to a child then we'll say a bit more.   The entire notion of considering atoms, electrons and nuclei as rigid little balls of stuff  where a little bit of momentum is passed from one to another in clearly defined separate interactions  is very limited.  We can spend time finding explanations that make things work based on this model but there's hardly any point.   There is probably just the one big wave function describing the behaviour of ALL the particles.  As such when a photon is absorbed by an electron at one place in the solid, it has affected the wave function which applies everywhere.    (we need to insert a pause here and think about that).
             ------ pause ----

       The wavefunction has changed (even if slightly) everywhere and will evolve with time according to the time dependant Schrodinger equation as usual.   In effect, the spread or dispersal of extra "jiggle" in the atoms may have started throughout the whole solid as soon as the photon was absorbed at any one place within it.   There does not need to be a "why" or "how", it just does.  Quantum mechanical effects are under no obligation to look like separate and sensible interactions between atoms. 

Best Wishes.

[alancalverd]

  A photon carries a certain amount of momentum.   It is a tiny amount.

Enter grumpy old pedant, stage left.

I think  "imparts" is better than "carries" since m_p = 0 but that's being pernickety. It took a while for supposed grownups to understand Einstein's explanation, but I hate lying to children - if they remember the truth, they may eventually understand it.

Don't be coy

There is a significant difference between speed and momentum

!   Momentum is mass x velocity, and a 5-year-old might just understand or at least remember "multiply".

Photon momentum in the visible spectrum is of the order of 10^-27 kg.m/s. The rest mass of an electron is about 10^-30  kg, so the subsequent electron velocity would be around 1000 m/s. About the speed of a bullet.

How do photons jiggle electrons? Electromagnetic radiation is just that, and an electron has a charge and a magnetic moment. It's easy to demonstrate magnetostatics and fairly easy to demonstrate magnetoelectrodynamics, so the answer is "why not?"

[Zer0 (OP)]

Was Refuted by views stating that an Electron does Not absorb a Photon.

And electron on its own doesn't (usually)  absorb a photon.
And electron in an atom or molecule can.

Thanks for Pointing that out.
That is Exactly the Mistake i made.
I misinterpreted what you said.
& In my googling keywords search i kept repeating the same mistake.

Rather than searching for " Atom absorbing Photon " i searched " Electron absorbing Photon ".

[Zer0 (OP)]

Just a reminder to all correspondents:

P.S. - Try explaining it like you would to a 5 year old.

Was a reference to Myself.
If you don't Believe me, check my profile.
Ha ha!

[Zer0 (OP)]

A Note to Eternal

I Appreciate your Detailed responses.

But i also Feel a sense of Guilt.

Perhaps your Contributions to this Forum are directly proportional with the length of your Grass lawn.

The More you spend time here, the more the Grass grows.

I Hope you are able to maintain a healthy equilibrium between your Online vs Offline worlds.

P.S. - if i were livin anywhere around, i would have cut that damn grass for free for U.
Thanks & Best Wishes!

[Eternal Student]

Hi.

I Hope you are able to maintain a healthy equilibrium between your Online vs Offline worlds.

    Thanks,   I'm off grass cutting duties for a while.    It's all too wet.

I think  "imparts" is better than "carries" since mp = 0

    Hmm....  I suppose the principle of conservation of momentum can be suspended until all photons have hit something.   Otherwise you have little choice except to say the photons do "have" or do "carry" that momentum.
   

How do photons jiggle electrons? Electromagnetic radiation is just that, and an electron has a charge and a magnetic moment. It's easy to demonstrate magnetostatics and fairly easy to demonstrate magnetoelectrodynamics, so the answer is "why not?"

      I do like that.   I don't think many children will argue or find a problem with it and it hadn't really crossed my mind when I was writing.   A classical e-m wave can accelerate charges it passes along the way and then just be gone or absorbed   (or vice versa -  an accelerated charge can generate e-m waves).
    Adults might find a problem if they try.   Most solids aren't metals and don't have electrons sloshing around and roaming free.  Zero's original question also did seem to lead on from the assumption that the photon had excited an electron to a new orbit.  This is a far more quantum version of things instead of a classical wave model for the e-m radiation.

Best Wishes.     

[alancalverd]

This brings us to the question of why the surface is black. Annoyingly, it is because the material absorbs visible photons!

So the electronic structure of whatever it is must have the capability of absorbing any and all photons in the range between 1.5 and 3.5 eV.  So we aren't talking about quantised energy levels but an effective continuum.

[alancalverd]

I suppose the principle of conservation of momentum can be suspended

May I remind my learned friend, with the greatest respect, that this is physics, not politics!