Correct Answer - Option 4 : x-rays
Concept:
The electromagnetic wave which helps in the study of structure of crystals is X-rays.
If a beam of x rays is passed through a crystal, it makes a pattern on a photographic plate.
The pattern is called crystallogram (the arrangement of the atoms each crystal has its own crystallogram). It reveals the crystal`s internal structure.
Crystals behave as diffraction slits, with dimensions equivalent to the wavelength of X-rays.
X-rays have wavelengths similar to the size of atoms, hence they are diffracted and the pattern is formed photographic plate.
