  We determined the refractive-index structure-factor $S_n(\bf k)$ from
shadowgraphs of fluctuations in a layer of a homeotropically aligned nematic
liquid crystal with negative dielectric anisotropy in the presence of an ac
voltage of amplitude $V_0$ applied orthogonal to the layer. $S_n(\bf k)$ had
rotational symmetry. Its integral $P(V_0)$ and amplitude $B(V_0)$ increased
smoothly through the Fr\'eedericksz transition at $V_0 = V_F$. Its inverse
width $\xi(V_0)$ and its relaxation rate $\Gamma_0(V_0)$ had cusps but remained
finite at $V_F$. The results are inconsistent with the critical mode at a
second-order phase transition.
