SKEDSOFT

Physics For Engineers - 1

                     ...................................... ( 3 )
 So the time taken by the second beam to reach and back to the plate P is,
                    
              .......................... ( 4 )

If the apparatus is rotated through 900, thus making the as cross-stream length (vertical) and as down-stream length (parallel to movement of earth) and the corresponding times are now designated as and respectively,

                 

The difference in transit time for both set of beams is,
                  
............... ( 6 )

                    ............... ( 7 )
The corresponding phase difference between interfering rays are,
                    

One fringe shift for a phase difference of 2.

 The no of fringes that shift due to a phase difference of is        

                                    

                     ............... ( 7 )

This would give = 0.4.  The experiment was performed day and night and at different times of year. Even though the sensitivity of the set up is to detect a shift of 0.01 fringe, no such shift was observed. Similar experiments were repeated by several groups but the result was same. The above experiment shows that the speed of light is constant in space irrespective of  the direction and speed of inertial frame.