362-week2
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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
michel2.mov
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 , the path is change by and the fringe pattern
is moved by one fringe.
Measuring the Refraction Index
Measuring the Refraction IndexLight for M1
Light for M2
Screen
Measuring the Refraction IndexLight for M1
Light for M2
Screen
Measuring the Refraction IndexLight for M1
Light for M2
ScreenN·
Nm
Na
Measuring the Refraction IndexL = thickness
n = index of refraction
Number of wavelengths in the block (2 times):Nm=2L/n=2Ln/
Number of wavelengths in same distance without block:Na=2L/=2L/
Phase change (in terms of wavelengths):N=Nm Na=2Ln/2L/2L/(n-1)
Measuring Distances
Phase change: N =2Ln/2L/2L/(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 ExperimentLight for M1
Light for M2
Screen
If light from M2 is delayed by t
Light for M1
Light for M2
ScreenL=t·c
L
The Michelson-Morley Experimentv
Mirror
Mirror
Beam Splitter
Screen
1
2
3
u12=c+v
u21=c-v
u13=u31=22 vc
t = t121 = t131 = Lv2/c3
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
Mirror
Mirror
Beam Splitter
Screen
1
2
3
ta = t121 = t131 = Lv2/c3
a = c t
a) v u12=c+v
u21=c-v
u13=u31=22 vc
The Michelson-Morley Experimentv
Mirror
Mirror
Beam Splitter
Screen1
2
3 tb = t121 = t131 = Lv2/c3
= a - b = Lv2/c2 ~ 0.2 m
b)
b = c t
u12=u21=
u13=c+v
u31=c-v
22 vc
The Michelson-Morley Experiment
The Michelson-Morley Experiment
Insert calculation of expected dL