Electrostatic corner-field exponent ($E\sim r^{\pi /\alpha -1}$)

If the lowest allowed angular harmonic has a nonzero coefficient, differentiating its potential gives the displayed field scale. The field vanishes at a right-angle recess, stays finite at a smooth face, and diverges at a protruding conducting corner whose exterior vacuum angle exceeds $\pi$. A rounded tip cuts off the ideal power law at its radius scale. If the first coefficient vanishes, the first nonzero higher harmonic determines the exponent instead.