CRYSTALLOGRAPHY IS BRANCH WHERE WE STUDY ABOUT GEOMETRY,PROPERTIES AND STRUCTURE OF CRYSTAL & CRYSTALLINE SUBSTANCE.

# MAIN LAWS OF CRYSTALLOGRAPHY ARE AS FOLLOWS:
 1.THE LAW OF CONSTANCY OF INTERFACIAL ANGLES (STENO'S LAW)
 2.LAW OF RATIONAL INDICES (HAUY'S LAW)

NOW,WE DISCUSS THESE LAWS ONE BY ONE....


 #THE LAW OF CONSTANCY OF INTERFACIAL ANGLES⇒

ACC.TO THIS LAW 
"THE SIZE OF FACES OR SHAPE OF CRYSTALS OF A SUBSTANCE MAY VARY WIDELY WITH CONDITIONS OF CRYSTALLIZATION BUT THE INTERFACIAL ANGLES B/W ANY TWO CORRESPONDING FACES ARE ALWAYS CONSTANT."  
 EXAMPLE: NaCl has always interfacial angle 90* whatever be shape




 these are NaCl crystals with different shape but angle same 90

#LAW OF RATIONAL INDICES⇒


ACC.TO THIS LAW
"THE RATIO B/W THE INTERCEPTS ON THE AXES FOR THE DIFFERENT FACES OF CRYSTAL CAN ALWAYS BE EXPRESSED BY WHOLE NUMBERS."

LET US CONSIDER A UNIT PLANE ABC ON AXES SUCH THAT OA=a,OB=b, OC=c on X,Y,Z AXES RESPECTIVELY.
NOW WE CONSIDER LMN PLANE THAT WE STUDY SUCH AS  OL=2a,OM=4b,ON=3c along X,Y,Z AXES.

(O is centre point where axes meet i.e. Origin point)
THE INTERCEPT RATIO OF PLANE LMN ON AXES IS⇛OL:OM:ON
⇛2a:4b:3c

these intercept are also called weiss indices of plane &


the coefficients of a,b,c are whole numbers.



 WEISS INDICES NEVER BE FRACTIONAL & INFINITE
BUT IF THESE ARE FRACTIONAL & INFINITE THEN THEY REPLACED BY MILLER INDICES.

updated soon.....