In this scenario, the acceleration \( a \) of the block on the inclined plane is given by the equation:
\[
a = g \sin \theta
\]
We are told that the acceleration is half of the acceleration due to gravity, so:
\[
\frac{g}{2} = g \sin \theta
\]
Solving for \( \theta \):
\[
\sin \theta = \frac{1}{2}
\]
\[
\theta = 30^\circ
\]
Thus, the angle of inclination \( \theta \) is \( 30^\circ \) for the block to have half the acceleration due to gravity.