Quantum Phenomena Quantum Phenomena IIII

Question & Answer SessionQuestion & 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.

Chris Parkes, April 2004

Is your handset working ?Yes

Graph: Is your handset working ?

How many magnetic substates (values of ml) does the electron d

orbital have ? 1

2

3

4

5

6

7

8

9

0

Graph: How many magnetic substates (values of ml) does the

electron d orbital have ?

States and their spectroscopic notation

n l m

1 0 0 1s

2 0

1

0

-1,0,1,

2s

2p

3

0

1

2

0

-1,0,+1

-2,-1,0,1,2

3s

3p

3d

4

0

1

2

3

0

-1,0,+1

-2,-1,0,+1,+2

-3,-2,-1,0,+1,+2

4s

4p

4d

4f

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

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

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

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

Graph: Black and white photographic film is more

sensitive to blue than red light. Hence, there are......

Red/Blue

• E=hf

• Which light has higher frequency ?

• That photon has more energy

• Number of photons in 1J =1J / Energy of 1 photon

Which is smaller ?An atom

A light wave (visible spectrum)

both are about the same

Graph: Which is smaller ?

Which is smaller?

• Smooth reflecting surfaces– Atom must be smaller than wavelength of light

• Sizes…..

• Bohr radius 52.9 pm

• Visible light 400-700 nm

• Electron microscope typically a few pm

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

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

Zeeman Effect• Observe energy spectrum of H atoms

• Now …add magnetic field

– Atoms have moving charges, hence magnetic interaction

– Spectral lines split (Pieter Zeman, 1896)

Angular momentum has made small contribution to energy (order 10,000th )

Fine Structure

Discrete Discrete statesstates

as as

Ang.mom. Ang.mom. quantizedquantized

Nature, vol. 5511 February 1897,

pg. 347

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

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

H Energy levels

Found an expression for EeV

nn

meE

22220

2

4 6.13

32

n = 2

n = 3

n = 4

Ionised atom

E0

1

E0hc

1ni

2 1n f

2

For transition

Ef

Emission

Photon

Energy levels depend upon Electron massand n

Spacing depends upon n values and E0

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

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

Continuous SpectrumEach atom will have different set of atomic levels- electron orbitsDifferent electron energy jumpsDifferent photon energiesDifferent line spectra

More types of atoms, more lines

Increase 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 spectrum of energy transitions and hence of photon energies

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

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

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

The protons and neutrons in the atomic nucleus are held together

byGravity

Electrostatic forces

The weak nuclear force

Magnetic forces

The confining effect of the orbiting electrons

None of the above

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

together by

A quark is aA 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

Graph: A quark is a

Quark

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

The age of the universe is roughly 15 thousand years times

ten to the power ?1

2

3

4

5

6

7

8

9

0

Graph: The age of the universe is roughly 15 thousand years times

ten to the power ?

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

Graph: Which of these statements best describes your opinion of

this session

QPII Tutorial Questions

Tutorial in week 19th –23rd April

1) From (updated) question sheet Question 1 & Question 4

2) In addition there is an on-line tutorial

Mastering Physicswww.masteringphysics.com

A web based physics tutorial system

If 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 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

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

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

c.parkes @ physics.gla.ac.uk

h.ward @ 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.

Quantum Phenomena II On-line tutorial

How useful do you find the use of handsets in your lecture?

Not at all useful

Not very useful

useful

very useful

extremely useful

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

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

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