Expalin Law of Rational indices

This Law states that the intercepts of any face of a crystal along the crystallographic axes are either equal to the unit intercept (a, b, c) or some simple whole number multiple of them, e.g., na, n’b, n’’c, etc. where n n’ n’’ are simple whole numbers.

Let OX OY and OZ represents the three crystallographic axes and let ABC be a unit plane. The unit intercepts will then be a b c.

 According to the above law the intercepts of any face such as KLM, on the same three axes will be simple whole number multiple of a b and c respectively. As can be seen from figure.