They confuse me. If someone tells me a plane has the index, say (233), it's very difficult for me to see where it intercepts the crystal axes. What are they good for?
But let's go back to the plane with index (233). I want to draw it in a coordinate system with the crystal axes a, b, and c. I know from my textbook that its coordinates in this coordinate system are (3,2,2) (that is, the plane intercepts the axes at 3a, 2b and 2c). But how do I get this information if I only know the index? I know how to get the index from knowing the coordinates, but vice versa seems to be more difficult.