Hello Jon

Ok, I'll make it qualitative and put "more than" in front of "cancel". If you consider the general trend of refractive index "from DC to daylight" or in this case to X rays, it decreases with increasing frequency and ultimately approaches unity. This goes against the grain of the visible spectrum where it increases with frequency.

In fact, the general downward trend of the real part of complex refractive index which describes light speed reduction (as opposed to the imaginary part which describes absorption) toward the high frequency end of the spectrum has a complicated spectral profile superimposed on it by a multitude of electron shell resonances, etc.

The anomalous positive dispersion gradient in the visible spectrum is a result of nearby electron resonances at UV frequencies. Any general effect over the whole EM spectrum (such as Martin's "refraction per cycle" or the inertial effect of electron mass which is responsible for the downward trend referred to above and to which my "less time to interact" comment refers) is irrelevant as it is swamped by the aforementioned resonance effects.

The notion of a fixed amount of refraction per cycle happening over a certain time or distance at a surface would result in refractive index being proportional to frequency. This is clearly not the case because 470nm blue light does not refract 40% more than 660nm red light. In actuality it only refracts 1% more.

Anyway, thank you for the correction. With my username I should be more careful! Consider my wrists duly slapped.

Cheers,

Chris