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