Physics 362
Modern Physics Seminars
Future arguments


Introduction to Astronomy


The Michelson-Morley Experiment


Consequences of relativity: relativity and time travel, relativity in
everyday life


Measuring distances in astronomy and the Hubble law


X-ray astrophysics


Nuclear Energy Production


Alternate energy sources (wind-mills, solar cells, etc.)


Principles of general relativity


Radiation processes


Neutrinos


Superconductivity


Cosmology
Today’s seminar

The failure of Classical Physics


Classical mechanics and electromagnetism
The Michelson-Morley experiment
The Michelson Interferometer
Fringe Interference
Parallel Fringes
Fringe position
A change in the
distance of one of the
two mirrors
introduces a phase
change between the
two light beams.
Fringe position
When the mirror is moved
by ½ l, the path is change
by l and the fringe pattern
is moved by one fringe.
Measuring the Refraction Index
Measuring the Refraction Index
Light for M1
Light for M2
Screen
Measuring the Refraction Index
Light for M1
Light for M2
Screen
Measuring the Refraction Index
Light for M1
Na
Light for M2
Nm
DN·l
Screen
Measuring the Refraction Index
L = thickness
n = index of refraction
 Number of wavelengths in the block (2 times):
Nm=2L/ln=2Ln/l
Number of wavelengths in same distance without block:
Na=2L/l=2L/l
 Phase change (in terms of wavelengths):
DN=Nm - Na=2Ln/l- 2L/l= 2L/l (n-1)
Measuring Distances
Phase change:
DN =2Ln/l- 2L/l= 2L/l (n-1)
 The length of an object
can be expressed in terms of
the wavelength of light!!!
For this experiment A. A. Michelson received the Nobel Price in 1907.
The Michelson Interferometer
1881
The Michelson-Morley Experiment
The Michelson-Morley Experiment
Light for M1
Light for M2
Screen
DL
If light from M2 is delayed by Dt
Light for M1
Light for M2
DL=Dt·c
Screen
The Michelson-Morley Experiment
v
Mirror
3
u12=c+v
u21=c-v
Beam Splitter
1
u13=u31=
c2  v 2
Mirror
2
Dt = t121 = t131 = Lv2/c3
Screen
The Michelson-Morley Experiment
How can we measure the delay?
There is no reference available that is at rest in ether!!!
The experimental apparatus is rotated
The Michelson-Morley Experiment
The Michelson-Morley Experiment
a)
v
Mirror
u12=c+v
u21=c-v
3
u13=u31=
Beam Splitter
1
Mirror
c2  v 2
Dta = t121 = t131 = Lv2/c3
2
Dla = c Dt
Screen
The Michelson-Morley Experiment
b)
v
u12=u21=
c2  v 2
u13=c+v
u31=c-v
Beam Splitter
Screen
1
3
Mirror
Dtb = t121 = t131 = - Lv2/c3
Dlb = c Dt
2
Mirror
 Dl = Dla - Dlb = 2Lv2/c2 ~ 0.2 mm
The Michelson-Morley Experiment
The Michelson-Morley Experiment
Insert calculation of expected dL