[Tex/LaTex] Drawing Lines in Tikz

tikz-pgf

I am relatively new to Tikz and am trying to draw a diagram with lines in it. Here is my MWE

\documentclass{article}

\usepackage{tikz}
\usetikzlibrary{matrix,positioning}
\usetikzlibrary{decorations.pathreplacing}

\begin{document}
\[
\begin{tikzpicture}
\draw (0,0.9) -- (3.0,0.9) -- (3.0,-0.9) -- (0,-0.9) -- (0,0.9);
\draw (1.0,-0.9) -- (1.0,0.9);
\draw (2.0,-0.9) -- (2.0,0.9);
\path (1.1,0.6) node (p9) {};
\path (1.1,0.2) node (p10) {};
\path (1.1,-0.2) node (p11) {};
\path (1.1,-0.6) node (p12) {};
\path (1.9,0.6) node (p13) {};
\path (1.9,0.2) node (p14) {};
\path (1.9,-0.2) node (p15) {};
\path (1.9,-0.6) node (p16) {};
\path (2.1,0.6) node (p17) {};
\path (2.1,0.2) node (p18) {};
\path (2.1,-0.2) node (p19) {};
\path (2.1,-0.6) node (p20) {};
\path (2.9,0.6) node (p21) {};
\path (2.9,0.2) node (p22) {};
\path (2.9,-0.2) node (p23) {};
\path (2.9,-0.6) node (p24) {};
\draw  (p9) to [bend left=10] (p17);
\draw  (p10) to [bend left=10] (p18);
\draw  (p11) to [bend left=10] (p19);
\draw  (p12) to [bend left=10] (p20);
\draw  (p13) to [bend right=10] (p21);
\draw  (p14) to [bend right=10] (p22);
\draw  (p15) to [bend right=10] (p23);
\draw  (p16) to [bend right=10] (p24);
\end{tikzpicture}
\]
\end{document}

This results in the following output

enter image description here

Can anyone explain why the curved lines don't appear to be hitting the correct nodes?

Edit: To clarify the situation, the question was concerned with why the lines were not apparently reaching the centre of the nodes in question. Solutions to this have been addressed in the answers below.

Best Answer

The curved lines hit the nodes but even empty nodes have a width and height. To show this the nodes in the second picture are drawn. Maybe you want to define coordinates instead of nodes like in the third picture:

enter image description here

Code:

\documentclass[margin=5mm,tikz]{standalone}

\usepackage{tikz}

\begin{document}
\begin{tikzpicture}[
  green!40!black,
  colored/.style={fill=#1!20,draw=#1!50!black!50}
]
\draw[help lines, step=0.5] (0,0)grid(2,1);
\path (0.5,0.5) node (p1) {};
\path (1,0.5) node (p2) {};
\draw (p1) to [bend left=10] (p2);
%
\begin{scope}[yshift=-1.1cm]
\draw[help lines, step=0.5] (0,0)grid(2,1);
\path (0.5,0.5) node[colored=red] (p3) {};
\path (1,0.5) node[colored=blue] (p4) {};
\draw (p3) to [bend left=10] (p4);
\end{scope}

\draw[dotted](p1.east)--(p3.east)(p2.west)--(p4.west);
%
\begin{scope}[yshift=-2.2cm]
\draw[help lines, step=0.5] (0,0)grid(2,1);
\path (0.5,0.5) coordinate (p5);
\path (1,0.5) coordinate (p6);
\draw (p5) to [bend left=10] (p6);
\end{scope}
\end{tikzpicture}
\end{document}
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