Extinction Shift Principle� : The Details
On the Measurability of the Wavelength and the Velocity of Waves
Note: Any observer would always note that the number of waves passing any fixed point per unit of time before the fixed interference "window" would equal the number of waves passing a fixed point per unit of time after the interference. It is the frequency of interference that is always the observable as a consequence of Galilean transformations and optical principles pertaining to the direct interference on the primary wave.
where neither the undisturbed velocity nor undisturbed wavelength on the left hand side of this equation is independently measurable. A measurement can only reveal the frequency of interference at the window, mirror or lens of the measuring apparatus. Always the extinction shifted wavelength, as a consequence of Galilean transformations of velocities and the principal axioms of the Extinction Shift Principle, is measured as
while the undisturbed primary wavelength is extinguished and is not measurable.
It is important to note once again that this is not a Doppler shift. This is the Fixed Window Axiom of the principal axioms given in the section on the Extinction Shift Theory Illustrated in the Appendix of the book on page 20A for the case of an approaching primary source. Similarly, the Fixed and Moving Mirror Axioms are treated on pages 21A and 22A and is applied directly to the famous and important Llord mirror experiment depicted on page 23A of the book in the section on Nullified Experiments in Optics. For details, see the next page On Principal Axioms of the Extinction Shift Principle.