We record the height of the crack surface as a function of position along one-dimensional cuts orthogonal to the crack for six different brittle materials. We find that the width w of this one-dimensional trace as a function of its length L behaves as w∼${\mathit{L}}^{\mathrm{\zeta }}$, where ζ=0.87(7). This result is in agreement with recent conjectures of a universal roughness exponent ζ for these materials.

• Received 26 August 1991

DOI:https://doi.org/10.1103/PhysRevLett.68.213