# Physics 362 Modern Physics Seminars Future arguments   Introduction to Astronomy   The Michelson-Morley Experiment   Consequences of relativity:

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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

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

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 Light for M2 Screen  N· NmNm NaNa

Measuring the Refraction Index L = thickness n = index of refraction  Number of wavelengths in the block (2 times): N m =2L/ n =2Ln/ Number of wavelengths in same distance without block: N a =2L/ =2L/  Phase change (in terms of wavelengths):  N=N m  N a =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

Light for M1 Light for M2 Screen If light from M2 is delayed by  t Light for M1 Light for M2 Screen  L=  t·c  L

The Michelson-Morley Experiment v Mirror Beam Splitter Screen 1 2 3 u 12 =c+v u 21 =c-v u 13 =u 31 =   t = t 121 = t 131 = Lv 2 /c 3

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

Mirror Beam Splitter Screen 1 2 3  t a = t 121 = t 131 = Lv 2 /c 3   a = c  t a) v u 12 =c+v u 21 =c-v u 13 =u 31 =

The Michelson-Morley Experiment v Mirror Beam Splitter Screen 1 2 3  t b = t 121 = t 131 =  Lv 2 /c 3   =  a -  b =  Lv 2 /c 2 ~ 0.2  m b)   b = c  t u 12 =u 21 = u 13 =c+v u 31 =c-v

The Michelson-Morley Experiment

Insert calculation of expected dL

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