Presentation on theme: "Quantum Phenomena II Question & Answer Session"— Presentation transcript:
1Quantum Phenomena II Question & Answer Session Chris Parkes, April 2004Quantum Phenomena II Question & Answer SessionUsing the handsetsA. Check handset is turned on -- green light on?B. Turn it over and read the 3 digit ID numberC. Point at a receiver (small box with red light on)D. Press the number of your choicesee your ID come up on the screenIf your ID doesn't come up, wait a few seconds then try again.Can change your vote, but don't keep sending unnecessarily as you will obstruct others' votes.
4How many magnetic substates (values of ml) does the electron d orbital have ? 123456789
5Graph: How many magnetic substates (values of ml) does the electron d orbital have ?
6States and their spectroscopic notation lm11s2-1,0,1,2s2p3-1,0,+1-2,-1,0,1,23s3p3d4-2,-1,0,+1,+2-3,-2,-1,0,+1,+24s4p4d4f
7If electrons did not obey the Pauli exclusion Principle then.... The electrons in an atom would annihilate with the protons in the nucleusThe electrons in an atom would all have the same energyThe electrons would repel each other preventing the formation of atomsThe electrons in an atom would have a continuous range of energies rather than lying in discrete levels
8Graph: If electrons did not obey the Pauli exclusion Principle then....
9Pauli Exclusion Principle No two electrons can occupy the same quantum mechanical stateActually true for all fermions (1/2 integer spin)Nothing to do with Electrostatic repulsionAlso true for neutronsDeeply imbedded principle in QMIf all electrons were in the n=1 state all atoms would behave like hydrogen ground stateNo chemistry – same properties
10Black and white photographic film is more sensitive to blue than red light. Hence, there are...... More photons in one joule of red light than in one joule of blueMore photons in one joule of blue light than in one joule of redThe same number of photons in one joule of red light as in one joule of blue
11Graph: Black and white photographic film is more sensitive to blue than red light. Hence, there are......
12Red/Blue E=hf Which light has higher frequency ? That photon has more energyNumber of photons in 1J =1J / Energy of 1 photon
13Which is smaller ? An atom A light wave (visible spectrum) both are about the same
15Which is smaller? Smooth reflecting surfaces Sizes….. Atom must be smaller than wavelength of lightSizes…..Bohr radius 52.9 pmVisible light nmElectron microscope typically a few pm
16We first learnt that the sun has a magnetic field By measurements made from spacecraft near the sunBy the direct effect of the sun’s magnetic field on magnetic compasses on earthBecause anything that has gravity must have magnetismThe effect the sun’s magnetism has upon the light we get from the sun.We have no knowledge of the sun’s magnetic field and no present way to get any
17Graph: We first learnt that the sun has a magnetic field
18Zeeman Effect Nature, vol. 55 11 February 1897, pg. 347 Observe energy spectrum of H atomsNow …add magnetic fieldAtoms have moving charges, hence magnetic interactionSpectral lines split (Pieter Zeman, 1896)Discrete statesasAng.mom. quantizedAngular momentum has made small contribution to energy (order 10,000th )Fine Structure
19If an electron was heavier spectral lines would be..... shifted towards blue and closer togethershifted towards red and closer togetherShifted towards blue and further apartshifted towards red and further apartshifted towards blue and same distance apartshifted towards red and same distance apartcloser togetherfurther apartunchanged
20Graph: If an electron was heavier spectral lines would be.....
21H Energy levels Found an expression for E Ionised atomEnergy levels depend upon Electron massand nn = 4For transitionn = 3n = 2E0Spacing depends upon n values and E0EfEmissionPhoton
22When light emitted by a glowing gas is passed through a prism, a line spectrum is produced. A continuous spectrum will be produced if the gas isA mixture of several kinds of atomsUnder low pressureUnder high pressureNone of these
23Graph: When light emitted by a glowing gas is passed through a prism, a line spectrum is produced. A continuous spectrum will be produced if the gas is
24Continuous Spectrum Each atom will have different set of atomic levels - electron orbitsDifferent electron energy jumpsDifferent photon energiesDifferent line spectraMore types of atoms, more linesIncrease the pressure, atoms crowd each otherDisturb each other’s atomic energy levelsNew orbits means new transition jumpsMore crowding , more energy jumps possibleAt high enough pressure have a continuous spectrumof energy transitions and hence of photon energies
25An atomic bomb was exploded inside a box that was strong enough to contain all the energy released by the bomb. After the explosion the box would weighMore than before the explosionLess than beforeThe sameNothing
26Graph: An atomic bomb was exploded inside a box that was strong enough to contain all the energy released by the bomb. After the explosion the box would weigh
27E=mc2 Mass is turned into energy in explosion So it weighs less ? What is left of the bomb weighs less.However, energy and mass are equivalentSo, considering the energy also the total weight is the same
28The protons and neutrons in the atomic nucleus are held together by GravityElectrostatic forcesThe weak nuclear forceMagnetic forcesThe confining effect of the orbiting electronsNone of the above
29Graph: The protons and neutrons in the atomic nucleus are held together by
30A quark is a A type of lepton A composite particle made from mesons and baryonsA star that will become a black holeA galactical clusterA type of soft cheese
32Quark[Its also a name for the fundamental particles of which mesons and baryons (e.g. proton,neutron) are made]
33The age of the universe is roughly 15 thousand years times ten to the power ? 23456789
34Graph: The age of the universe is roughly 15 thousand years times ten to the power ?
35Which of these statements best describes your opinion of this session A waste of timeFun but not worthwhile, learnt less than in a lectureWould like a few questions like this put in one lecture per courseWould like a few questions like this put in half of the lecturesWould like a few questions like this in all lecturesAll lectures should be like this one
36Graph: Which of these statements best describes your opinion of this session
37QPII Tutorial Questions Tutorial in week 19th –23rd AprilFrom (updated) question sheetQuestion 1 & Question 4In addition there is an on-line tutorial
38Mastering Physics www.masteringphysics.com A web based physics tutorial systemIf you bought Young & Freedman 11th editionyou have free use of this system.If you don’t have free use then don’t pay as we are onlydoing this one on-line tutorial this yearGo to website and register using the registration key that came withyour bookYou will be asked for the course code this is:MPWARD0005You will have two assignmentsIntroduction to using the system, Quantum Phenomena II
39Quantum Phenomena II On-line tutorial 3Optional Introduction to the system practice questionsLearn to use the systemTry wrong answersTry using hints3 Optional QP practice questionsLearn some physics!4 Assignment QuestionsThe system will give you a mark for these.Only two tries allowed.Bonus marks if you don’t use hintsThe assigned questions will probably take you around one hour.The questions are similar to those on the question sheet / in the bookNot an exam – please use your books, notes if you wish as you would when doing normal tutorial question
40Quantum Phenomena II On-line tutorial We are thinking of adopting this tutorial system for the new students in October so we would like to know your opinions.If you use it please could you provide feedback tophysics.gla.ac.ukphysics.gla.ac.ukIf you have any difficulties in accessing the system please can you also let us know.We will give a prize (book token) to the student who gets the best mark and provides the most useful feedback.
41How useful do you find the use of handsets in your lecture? Not at all usefulNot very usefulusefulvery usefulextremely useful
42What was, for you, the balance of benefit vs What was, for you, the balance of benefit vs. disadvantage from the use of the handsets in your lecture?Definite negative net valueMore disadvantage than benefitNeutralBenefits outweigh any disadvantagesDefinitely benefited
43Which of the following do you consider to be the most important benefit (if any) of the use of handsets in your lecture?Gives me an idea of how well everyone else is doing.Checks whether I am understanding the course material as well as I thought I wasAllows me to answer privately without others knowing how I voted.Allows lecturers to identify problem areasMakes me think more about the course material during my lecturesIt's funIt makes the lectures more interactiveOther benefitDon't consider there are any benefits
44Which of the following do you consider to be the second most important benefit (if any) of the use of handsets in your lecture?Gives me an idea of how well everyone else is doing.Checks whether I am understanding the course material as well as I thought I wasAllows me to answer privately without others knowing how I voted.Allows lecturers to identify problem areasMakes me think more about the course material during my lectures.It's funIt makes the lectures more interactiveOther benefitDon't consider there are any benefits