I am doing research on the hitting probability of various sets (eg. 3D convex) and specifically how changes in perimeter/surface area change the hitting probability. By hitting probability I mean $P(B[0,t]\cap A\neq \varnothing$ for some t). Say we have two planes in $\mathbb{R}^{3}$, one with greater area than the other and ,I suppose, equidistant from the origin. Then given a brownian motion starting from the origin, I want to get the hitting probability of each plane. I suppose the larger surface area plane will have a great probability. But what would be a rigorous way of proving that? My attempt so far is to work with the Brownian motion coordinates and define stopping times. Also, can you provide some books/papers that expose Brownian motion and surface area for more general sets? Thnx