Step 1: Applying Bragg’s law.
The condition for diffraction in crystals is given by Bragg’s equation:
\[
n\lambda = 2d \sin\theta
\]
where \(n\) is order of diffraction, \(\lambda\) is wavelength, \(d\) is interplanar spacing, and \(\theta\) is diffraction angle.
Step 2: Substituting given values.
Here, \(n = 1\), \(\lambda = 9 \,\AA\), and \(\sin 60^\circ = 0.866\). Substituting:
\[
1 \times 9 = 2d \times 0.866
\]
Step 3: Simplifying equation.
\[
9 = 1.732d
\]
Step 4: Solving for \(d\).
\[
d = \frac{9}{1.732} \approx 5.2 \,\AA
\]
Step 5: Final interpretation.
Thus, the spacing between crystal planes is approximately \(5.2 \,\AA\), consistent with Bragg diffraction conditions.
Final Answer:
\[
\boxed{5.2 \,\AA}
\]