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Quantum Phenomena II Question & Answer Session

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1 Quantum Phenomena II Question & Answer Session
Chris Parkes, April 2004 Quantum Phenomena II Question & Answer Session Using the handsets A. Check handset is turned on -- green light on? B. Turn it over and read the 3 digit ID number C. Point at a receiver (small box with red light on) D. Press the number of your choice see your ID come up on the screen If 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.

2 Is your handset working ?
Yes

3 Graph: Is your handset working ?

4 How many magnetic substates (values of ml) does the electron d orbital have ?
1 2 3 4 5 6 7 8 9

5 Graph: How many magnetic substates (values of ml) does the electron d orbital have ?

6 States and their spectroscopic notation
l m 1 1s 2 -1,0,1, 2s 2p 3 -1,0,+1 -2,-1,0,1,2 3s 3p 3d 4 -2,-1,0,+1,+2 -3,-2,-1,0,+1,+2 4s 4p 4d 4f

7 If electrons did not obey the Pauli exclusion Principle then....
The electrons in an atom would annihilate with the protons in the nucleus The electrons in an atom would all have the same energy The electrons would repel each other preventing the formation of atoms The electrons in an atom would have a continuous range of energies rather than lying in discrete levels

8 Graph: If electrons did not obey the Pauli exclusion Principle then....

9 Pauli Exclusion Principle
No two electrons can occupy the same quantum mechanical state Actually true for all fermions (1/2 integer spin) Nothing to do with Electrostatic repulsion Also true for neutrons Deeply imbedded principle in QM If all electrons were in the n=1 state all atoms would behave like hydrogen ground state No chemistry – same properties

10 Black 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 blue More photons in one joule of blue light than in one joule of red The same number of photons in one joule of red light as in one joule of blue

11 Graph: Black and white photographic film is more sensitive to blue than red light. Hence, there are......

12 Red/Blue E=hf Which light has higher frequency ?
That photon has more energy Number of photons in 1J = 1J / Energy of 1 photon

13 Which is smaller ? An atom A light wave (visible spectrum)
both are about the same

14 Graph: Which is smaller ?

15 Which is smaller? Smooth reflecting surfaces Sizes…..
Atom must be smaller than wavelength of light Sizes….. Bohr radius 52.9 pm Visible light  nm Electron microscope  typically a few pm

16 We first learnt that the sun has a magnetic field
By measurements made from spacecraft near the sun By the direct effect of the sun’s magnetic field on magnetic compasses on earth Because anything that has gravity must have magnetism The 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

17 Graph: We first learnt that the sun has a magnetic field

18 Zeeman Effect Nature, vol. 55 11 February 1897, pg. 347
Observe energy spectrum of H atoms Now …add magnetic field Atoms have moving charges, hence magnetic interaction Spectral lines split (Pieter Zeman, 1896) Discrete states as Ang.mom. quantized Angular momentum has made small contribution to energy (order 10,000th ) Fine Structure

19 If an electron was heavier spectral lines would be.....
shifted towards blue and closer together shifted towards red and closer together Shifted towards blue and further apart shifted towards red and further apart shifted towards blue and same distance apart shifted towards red and same distance apart closer together further apart unchanged

20 Graph: If an electron was heavier spectral lines would be.....

21 H Energy levels Found an expression for E
Ionised atom Energy levels depend upon Electron mass and n n = 4 For transition n = 3 n = 2 E0 Spacing depends upon n values and E0 Ef Emission Photon

22 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 A mixture of several kinds of atoms Under low pressure Under high pressure None of these

23 Graph: 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

24 Continuous Spectrum Each atom will have different set of atomic levels
- electron orbits Different electron energy jumps Different photon energies Different line spectra More types of atoms, more lines Increase the pressure, atoms crowd each other Disturb each other’s atomic energy levels New orbits means new transition jumps More crowding , more energy jumps possible At high enough pressure have a continuous spectrum of energy transitions and hence of photon energies

25 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 More than before the explosion Less than before The same Nothing

26 Graph: 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

27 E=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 equivalent So, considering the energy also the total weight is the same

28 The protons and neutrons in the atomic nucleus are held together by
Gravity Electrostatic forces The weak nuclear force Magnetic forces The confining effect of the orbiting electrons None of the above

29 Graph: The protons and neutrons in the atomic nucleus are held together by

30 A quark is a A type of lepton
A composite particle made from mesons and baryons A star that will become a black hole A galactical cluster A type of soft cheese

31 Graph: A quark is a

32 Quark [Its also a name for the fundamental particles of which mesons and baryons (e.g. proton,neutron) are made]

33 The age of the universe is roughly 15 thousand years times ten to the power ?
2 3 4 5 6 7 8 9

34 Graph: The age of the universe is roughly 15 thousand years times ten to the power ?

35 Which of these statements best describes your opinion of this session
A waste of time Fun but not worthwhile, learnt less than in a lecture Would like a few questions like this put in one lecture per course Would like a few questions like this put in half of the lectures Would like a few questions like this in all lectures All lectures should be like this one

36 Graph: Which of these statements best describes your opinion of this session

37 QPII Tutorial Questions
Tutorial in week 19th –23rd April From (updated) question sheet Question 1 & Question 4 In addition there is an on-line tutorial

38 Mastering Physics www.masteringphysics.com
A web based physics tutorial system If you bought Young & Freedman 11th edition you have free use of this system. If you don’t have free use then don’t pay as we are only doing this one on-line tutorial this year Go to website and register using the registration key that came with your book You will be asked for the course code this is: MPWARD0005 You will have two assignments Introduction to using the system, Quantum Phenomena II

39 Quantum Phenomena II On-line tutorial
3Optional Introduction to the system practice questions Learn to use the system Try wrong answers Try using hints 3 Optional QP practice questions Learn some physics! 4 Assignment Questions The system will give you a mark for these. Only two tries allowed. Bonus marks if you don’t use hints The assigned questions will probably take you around one hour. The questions are similar to those on the question sheet / in the book Not an exam – please use your books, notes if you wish as you would when doing normal tutorial question

40 Quantum 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 to physics.gla.ac.uk physics.gla.ac.uk If 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.

41 How useful do you find the use of handsets in your lecture?
Not at all useful Not very useful useful very useful extremely useful

42 What 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 value More disadvantage than benefit Neutral Benefits outweigh any disadvantages Definitely benefited

43 Which 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 was Allows me to answer privately without others knowing how I voted. Allows lecturers to identify problem areas Makes me think more about the course material during my lectures It's fun It makes the lectures more interactive Other benefit Don't consider there are any benefits

44 Which 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 was Allows me to answer privately without others knowing how I voted. Allows lecturers to identify problem areas Makes me think more about the course material during my lectures. It's fun It makes the lectures more interactive Other benefit Don't consider there are any benefits


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