studiot

Thank you for your answers to the questions. Yes I think from your answers you have correctly understood the questions. However you questions demonstrate that you need to understand the basics better. This is not a personal criticism but an attempt to help you. Diffraction and interference are different phenomena. Interference ony occurs when two separate waves overlap (occupy the same space). Changes of direction (spreading) of the waves is not involved. Diffraction is the result of a single wave interacting with a wave blocking object. It is the name given to the spreading of (single) waves when they pass through apertures or around objects. Until recently it has not been possible to show interference from two different light sources, but has been possible with other waves. That is way classical interference experiments split the light from a single source. The slit(s) experiment require a single plane wave in the space between the source and the slit(s) barrier. So interference is not possible or observable in that space. Insertion of an observation screen will show an even illumination. Insertion of a blocking object may show diffraction effects around its edges or in its shadow zone. With a single slit, the result of the passage of the wave depends upon the geometry of both the wave and the slit. Some results are also dependent upon the distances of the source and observing screen from the slits. For instance this distinguishes Fraunhofer and Fresnel diffraction. All of these phenomena are well tested experimentally, some have been known for hundreds of years. As regards the difference between the wave and photon models of light consider the quantity I, the intensity of illumination at any point on the screen. We have for photons [math]I = nh\nu [/math] And for waves [math]I = {\varepsilon _0}c{E^2}[/math] The key point here is that for either model the I must be equal as they refer to the same observable quantity.

Yes Markus has nailed it. I was wondering whether to recommend the Beiser book to you anyway but here is the contents page. Note carefully that his choice of chapters and their order. 1. 2. Particle properties of waves. 3. Wave properties of particles. 4. It really is a well thought out book. In particular it describes the observations and experiments that led to the 'quantum theory of light' really well. So let me ask you some simply physics question. In the single slit or double slit experiment, is diffraction or interference possible in the region before the slit barrier i.e. can diffraction or interference be observed ? Are both interference and diffraction possible in a) The single slit ? b) The double slit ?

It is not a question of semantics. You plain and simple misquoted the man. You really owe him an apology.

Hello, and welcome. You opening post reminds me of when I was 12 and wrote to Patrick Moore because I did not understand the greenhouse effect and he wrote me a letter not only beautifully explaining it to me but also encouraging me to keep thinking and questioning. So it is with you and infinity. Infinity is not only a very stange beast it is also a many headed one. And each head is different. The light that is worrying is infinitely spread out, if the size of the universe is infinite. So there will be no flood of light at any point, no matter how much light there is in total. In fact we now know that what we see is not totally black (ie zero light) but there is a residual amount at a very low level called the CMB or background radiation. Additionally there isobviously more light when we look at a nearby source of light, and the closer the source is the brighter is seems. Does this help ?

I really am amazed how completely you have just proved my words in your desire to argue, instead of listen. You have completely twisted swanson't words round in your reply to me. How can "will not interact" (swansont) ever mean "should interact" (bangstrom) ? Just to continue my suggestion that you should leran the basics properly here is a really good book by Arthur Beiser (fourth edition or later) Concepts of Modern Physics - McGraw-Hill. The book lays out all the areas of modern physics in a way that can be easily understood with excellent summaries and diagrams and contains the answers to many of the questions you seem to want to debate.

A perfect example of why you are not listening to others. Which is particularly counterproductive here as swansont has graced you with far more detailed answers than his usual terse responses. I really suggest you stop looking for esoteric special cases and start learning the basics.

@md65536 Yeah you got it +1

Organic light emitting polymers. PS I fully support your other efforts here. +1

Well I have not got it. Are we talking about electric or magnetic effects of covalent bonds ? These are quite separate and due to separate mechanisms. Many substances that are covalently bonded conduct electricity, due to electrons being able to reach the conduction bands. OLEPS are a good example. There is a type of covalent bond called a dative bond which enjoys magnetic effects due to the separation of charge. Please clarify which we are talking about, magnetic or electric effects as each deserve a thread of their own.

It's been some while since we had a weeend puzzle to chew on so here is a new one. You enter the bar and are offered a 1200 ml jug of beer on the condition that you divide the beer exactly into halves by pouring it into a number of jugs until you have exactly half in one of them. You are provided with two empty jugs of 800 and 500 ml capacity. None of the jugs have any markings to indicate volume. Other rules are that you may not discard any beer or use any further containers or weigh anything. What is the minimum number of pouring steps to achieve this and what are they ? Please put answers in a 'spoiler', available at the end of the input icon bar as an eye symbol.

+1

Using the present continuous is perfectly correct and acceptable in the right context. As a monument inspector I am often visiting old monuments in the course of my duties. A continuous process that is still ongoing in the present and will do so in the future.

Oh ? About a dozen exchanges in thread between yourself and swansont sure fooled me into thinking you two were have a discussion. I did not say it was your thread. Thank you for clarifying your position.

Thank you for your replies, but remember my intention here is not to interfere in your discussion with swansont. It is to help geordief beter understand waves and the slits experiment. So I will just ask you the simple question how do you view light as a wave when you are working at the one photon at a time scale as I believe you are trying to do ?

What a pity no one else is prepared to give way even a tiny bit here and accept that someone else has something valid worth stating. Perhaps you are all totally correct. That would be the day

Yes, let's be clear as it is my turn to respond in our discussion on this. This discussion is sparate from the one with iNow, who said something different and I am answering separately. You did indeed say this and I quoted you in my original challenge. You have since amplified your proposition Yes I have never credited you with saying everything is quantised. But you do seem to be only considering one aspect of quantum theory and also implying that other aspects are insignificant. This latter is not the case. The commutation of observables only occurs directly in Heisenberg matrix theory, from which it arises quite naturally mathematically and leads to quantisation. But coherence and decoherence do not refer to these variables, but to wave functions which arise in Schrodinger wave theory as partial differential equations in the (quantum) wave function. The quantisation here again arises quite naturally in the choosing of integer multiples of solutions, but there is no commutation involved and further we obtain the familiar discreteness being talked about. You are correct in saying that the devil is in the detail, in the guise of the boundary conditions. A further point is that there are many (very) important quantities in Physics which are not quantised, for instance many dimensionless numbers, Avogadro's number, etc Finally not just for you but a general point, Physics is far from all of Science. So for instance the biological difference between a coal tit, a blue tit, a great tit and so on, and their classification, has nothing whatsoever to do with quantum theory.

I should start by understanding covalent bonds. Firstly there is not one shared electron in a covalent bond but two. Secondly these two electrons do not oscillate from one atom to the other. In truth, once bonded there are no 'atoms' in a covalently bonded molecule.

No idea what this is ?

Let us say that you have a simple equation f(x) = 3x -7 The equals sign here is an identity. This means it is true for any and all values of x. Or that f(x) and 3x + 7 are identical, and may be substituted for each other in any application. Now let us say that you have an equation 3x-7 = 0 There is only one value of x which satisfies this equation and any other value you assign to x does not. That is just an equality for x = 7/3 Does this help ?

No one has said you are not wanted. But I certainly find your attitude unattractive, and I expect others do as well. You asked a question and were answered with a simple technical example You were offered also some help with the workings of this website, that you have not bothered to acknowledge. So my advice is to ask your questions, contribuute where you can, and loose the attitude.

You have no evidence for what I have or have not read. So why not just pony up with your explanation ? By the way I seem to be having at least three different discussions with three different members in this thread. Here, I am responding to your connection of the phrase 'everything is' (as I have already explained) to the my separate discussion with Markus. That is still a matter of open debate in the scientific world. If you mean that everything is open for debate then I apologize for the misunderstanding. If you mean the everything is or is not quantised, which is the subject of my discussion with Markus, then please confirm this. I will reply to Markus separately as he seems to have missed some important points or incorrectly dismissed them as unimportant. I sincerely hope you do not mean that everything in Science or even everthing of importance in Science, is quantised, as that impression is easy to dispel by asking for the quantisation of Avogadro's number.

No it is not subject specific and my answer is not subject specific either. Self study is wonderful and the higher the level you go the more you have to study that way rahter than a course structured by others. However in my view the real difference between school and self study is that school (should) offers marked work or work guidance. That is the opportunity to get soemthing wrong and then to discuss with your teacher how and why you got it wrong and then to correct it. Or even just the simple yeah you did those well 10/10. With self study most people cannot do this for themselves. Coming to a forum such as this one is a great way to extend the base you are gaining from schoolwork by discussion with others here. If you are lucky you can also have great discussions with your classmates. It is often said that you can learn almost as much from your classmates as your teachers, I certainly did and was lucky that way. So get the best you can out of school and extend it outside.

First of all, the 5 posts rule only applies in the first 24 hours. This is good anti troll/anti spam measure. I see you have been a member longer than 24 hours and have made 7 posts, so you are past that. Secondly you posted, then deleted, some answer to my question to you. It would be nice if you would answer that one, especially as you are pushing Zap for some answer to your own.

Waiting a long time ? Only till my response. What 'love' do you thing a single celled organism experiences and where does that 'love' come from ? Perhaps your are right there is no purpose, but I like your idea of hedging one's bets when we simply don't know the answer. +1

Yes I get that you are trying to understand and not trying to force through a particular point of view. +1 So starting with a plane wave (do you know that all the slit experiments start with a plane wave, not any other sort ?) There are no slits and not screens or other 'detectors' So the plane wave just travels or progresses in the space. An 'observer' will see (detect) nothing at all ( as he has no means to detect the wave) Now introduce a screen detector. The observer will see a light on the screen, but no interference pattern. He will see this because the screen interacts with the plane wave (blocking it in this case) and illuminates. The screen therefore allows an observer to detect the wave. Now introduce a suitable slit or slits and the observer's view on the screen will change. Depending upon the size and configuration of the slits an interference pattern may observed on the screen. This is because the interaction of the slit array is not blocking but modifying the wave, changing it from planar to circular or spherical. Is the terminology becoming clear ?