# Reciprocal lattice points and diffraction peaks

I am having a issue with the concept of what this question is asking.

Question

For a FCC crystal describe all the reciprocal lattice points corresponding to the two diffraction peaks.

Here is my issue, it how I relate the lattice points to the diffraction peaks, as I am unaware of any method to do this.

My method thus far in solving is as follows.

1. The reciprocal lattice of a FCC is a BCC so from this I can find the geometrical structure factor.

2.From geometrical structure it is seen that allowed reflections that would correspond to the first two diffraction peaks are {110} and {200}, for which are a family of planes.

1. Planes that would allow for the peak are: (110) (101) (011) and (200) (020) (002).

And this is where my issue lies, is that these are planes represented by miller indices which are not lattice points. Have I missed something vital here or are my calculations completely wrong? I just cant understand how you related the points to the diffraction peaks.

I know the planes are represented by miller indices which a inverse of x y and z coordinates but they don't necessarily have to relate to lattice points