Final answer:
X-rays are used to examine crystal lattices because they have wavelengths that are short enough to resolve the small structures within the lattices. This is known as X-ray diffraction. In CT scanners, the limitation of detecting details smaller than 0.5 mm is indeed due to the wavelength of the X-rays.
Step-by-step explanation:
Crystal lattices can be examined with X-rays but not UV because X-rays have shorter wavelengths that can resolve smaller structures. The typical wavelength of X-ray photons is about 0.0228 nm, which is on the order of the distance between neighboring atoms in crystals, a few angstroms (Å). This allows for the process known as X-ray diffraction to occur, where X-rays are scattered by the atoms in the crystal to produce patterns that reveal the structure of the crystal.
Regarding CT scanners, they do not detect details smaller than about 0.5 mm due to the limitation imposed by the wavelength of X-rays used. If the structures are smaller than the wavelength of the X-rays being used, they will not create a detectable diffraction pattern and thus cannot be resolved.