When white light is refracted in a prism, we can see that blue color has the strongest refraction: the shorter the wavelength, the strongest the refraction. But the electromagnetic radiation with very short wavelength (X-rays) are not refracted by an amorphous solid such as glass: most part of the radiation goes straight through the glass with no interaction. Since the behaviour is so different in the optical and the X-ray regions, I wonder what happens between both, i.e, in the UV region. Does the refractive index increase with the frequency of the wave until some point and then fall quickly, or what happens exactly? Thanks in advance!