The correct answer is X-Rays wavelength. Explanation & Key Takeaways: • X-Rays are used to study the crystal structure of materials. • The wavelength of X-rays ranges from 0.01 nm to 10 nm, which is suitable for analyzing the atomic and molecular structure of crystalline solids. • When X-rays interact with a crystal, diffraction occurs according to Bragg's law: • nλ = 2d sinθ, where λ is the wavelength, d is the spacing between planes in the atomic lattice, and θ is the angle of incidence. • This diffraction pattern helps scientists determine the arrangement of atoms within the crystal. Related Concepts: • Ultraviolet wavelengths are not suitable for crystal structure analysis as their wavelength is too long for atomic-scale resolution. • Gamma rays have extremely short wavelengths but are less commonly used due to difficulty in handling and lower resolution compared to X-rays for crystallography. • Infrared wavelengths are used for other purposes, such as studying vibrational modes of molecules, but not for crystal structure determination.