Modern Physics

1
Modern Physics
2
Modern Physics

• 323 Fall 2008
• Course Description
• This course presents an introduction to some
  aspects of our understanding of light and matter.
• Topics covered will include
• The Special Theory of Relativity
• The Bohr Atom
• Wave Mechanics
• Elements of Quantum Mechanics
• Atomic Theory
• Molecules
• The Solid State

3

• Instructor
• Prof. ColmT Whelan (www.physics.odu.edu/whelan).
• Office hours M W F 3-4 pm in room 125 and by
  appointment.
• Students are strongly encouraged to come and seek
  help in person but
• questions are also answered by email
  (cwhelan_at_odu.edu) or phone [phone].
• Lecture notes and other material will be made
  available on the web within the folder
• www.physics.odu.edu/whelan/MP2008/

4

• Course Requirements There will be two
  examinations, Mid-term, worth 35, and final,
  worth 50 of the grade. There will be 3 homework
  assignments, worth 15 of the grade.
• The first examination will take place in the
  usual class room at the usual time(2.00pm-3.00pm)
  on October the 17th
• The final examination will take place on December
  10th in the usual class room(1230pm -330pm)
• There will be no classes on September 1st and
  26th
• There will be no classes on October 13th, 15th
• There will be two extra classes (homework and
  past exam questions) on October 9th and December
  4th
• Problem sheet 1 will be distributed in class on
  Monday August the 25th and solutions should be
  returned in class on Monday September the 22nd
  Problem sheet 2 will be distributed in class on
  Monday September the 22nd and solutions should be
  returned in class on Monday October the 20th
• Problem sheet 3 will be distributed in class on
  Monday October the 20th and solutions should be
  returned in class on Monday November the 24th
• Late work will not usually be accepted.

5
Text books

• Landshoff,Metherell and Rees,
• Essential Quantum Physics, CUP
• is required
• For second part of course.
• For first part(special relativity)
• Kleppner and Kolenkow
• An Introduction to Mechanics, McGraw-Hill
• And
• Rindler
• Special Relativity,OUP
• are recommended

6
Modern Physics
20th Century Physics
Stupid Name
7
(No Transcript)
8
(No Transcript)
9
(No Transcript)
10

• The more important fundamental laws and facts of
  physical science have all been discovered, and
  these are now so firmly established that the
  possibility of their ever being supplanted in
  consequence of new discoveries is exceedingly
  remote . . . Our future discoveries must be
  looked for in the sixth place of decimals.
• Albert A. Michelson, 1894

11
(No Transcript)
12

• What would you see if you were riding on a beam
  of light?

13
The Michelson-Morely Experiment

• Maxwells electromagnetic theory (1861) predicted
  that electromagnetic waves in empty space would
  travel at

The speed of light
14
Problem

• normal waves are a disturbance in a medium
• Water waves
• Sound waves

15
(No Transcript)
16
Encase in glass pump out air
17
Sound stops
18

• Air is the medium for sound

19
(No Transcript)
20
Pump out air
21
No effect
22

• Air is not the medium for light

23
What is the medium?

• Maxwell and his contemporaries postulated that
  there was a magic fluid that permiated all space
  the ether
• It needed to have very special properties

24

• It had to be immensely rigid to give such an
  enormous speed
• It had to be insubstantial enough not to
  interfere with motions of the planets

25

• The earth circles the sun at 3 ?104 m/s
• This should change the apparent speed of light.

26
Suppose that light makes a round trip between two
mirrors separated by a distance L
L
The appartus is moving through the ether to the
right with speed v
27
Relative to the appartus the ether is moving to
the left
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
Wave properties

• Suppose we have two wave fronts
• of equal amplitude .

32
If they are in phase

33
If they are exactly out of phase

34
(No Transcript)
35
(No Transcript)
36

• The light travel from the source to a beam
  spliter(half silvered mirror) half travels down
  one arm of the apparatus straight on to mirror M1
  where it is reflected back to A and then to the
  observer The other half of the beam is deflected
  along arm2 to the second mirror where it is
  reflected straight back to the observer.

37

• If the length of Arm1Arm2
• then the velocity of the earth w.r. to the
  ether should mean that there is a phase
  difference between the two beams when they come
  together.
• For a nice video from Caltech
• Caltech The Mechanical Universe - 41 - The
  Michelson-Morley Experiment

38
Result

• To a very high degree of precision
• The ether could not be detected
• The speed of light was constant

39
Some Mathematics

• Complex numbers
• Matrices

40
(No Transcript)
41
(No Transcript)
42
(No Transcript)
43
(No Transcript)
44
(No Transcript)
45
(No Transcript)
46
(No Transcript)
47
(No Transcript)
48
Rz
q
49
(No Transcript)
50
(No Transcript)
51
(No Transcript)
52
(No Transcript)
53
Trigonometric relations