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.
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
0
1
2
0
-1,0,+1
-2,-1,0,1,2
3s
3p
3d
0
1
2
3
0
-1,0,+1
-2,-1,0,+1,+2
-3,-2,-1,0,+1,+2
4s
4p
4d
4f
3
4
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
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
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 E
me4
 13.6
E

eV
2 2 2 2
2
32  0  n
n
Energy levels depend upon Electron mass
and n
For transition


E
1
1 
0  1

 2
2


hc 
n
n
f 
 i
n=4
n=3
n=2
Spacing depends upon n values and E0
Photon
Ef
Emission
Ionised atom
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 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
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
2
E=mc
• 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
by
Gravity
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 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
Graph: A quark is a
Quark
• [Its also a
name for the
fundamental
particles of
which
mesons and
baryons
(e.g.
proton,neutr
on) 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 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
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
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
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.
How useful do you find the use
of handsets in your lecture?
Not at all useful
Not very useful
useful
very useful
extremely useful
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
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
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