Visible frequency spectrometers measure wavelengths, or wavenumbers, not frequencies, which is why all the early Omnia Opera papers with Michelson interferometry in the far infra red are expressed in wavenumbers in accordance with National Physical Laboratory standard practice. We worked directly with the National Physical Laboratory, whose staff loaned Mansel Davies one of their interferometers. However absolute frequencies of visible frequency lasers can be measured with great accuracy, and so can absolute wavelengths, so this provides an accurate measurement of c in the vacuum or v in a medium. So the data sent over by Gareth are in wavelengths, converted to frequencies by use of c. Therefore the standard physicists would argue that what is being observed is a wavelength shift and not a frequency shift. However, if the phase velocity is the same, (c or v) then the wavelength shifts are equivalent to frequency shifts. In the far infra red we always used one wavenumber equals 30 GHz, so wavelength and frequency were used interchangeably to link up with dielectric studies which always used frequency. The conversion of one wavenumber to 30 GHz takes place with lambda = c / f, so the use of c by Gareth follows this practice. The key point theoretically is that the old dogma blatantly violates conservation of energy and momentum. The old dogma asserted that the incident, refracted and reflected frequencies are all the same, but the wavelengths and phase velocities change. This assertion was based on the use of boundary conditions, and a particular solution of those conditions chosen to make sure that the frequencies were the same. So it was a circular argument. In notes for UFT279 I have shown that Snell’s Law can be obeyed when the frequencies are not the same. Conservation of energy and momentum was never considered in the old dogma, e. g. Jackson’s treatment in “Classical Electrodynamics”. The Planck Law is based on frequency, and not wavelength. So the Evans / Morris shifts are very large shifts whether they be measured by spectrometers in wavelengths, or by absolute frequency measurement.