Isotropic solids have the same value of the reflective index in all the direction. All isotropic solids are amorphous solids. Amorphous solids cut into two pieces with irregular surfaces. Therefore, amorphous solids do not show cleavage. Anisotropic solid is a solid material in which the physical properties do not depend on its orientation.

Explanation: Amorphous solids do not show cleavage property because of an irregular arrangement of particles. When amorphous solids are cut with the sharp-edged tool the newly generated surfaces are irregular and not smooth.