If one surface of a lens is plano and the other is a plus surface, the lens is referred to as:

A lens that has one plano (flat) surface and one convex surface is described as planoconvex. The term "planoconvex" precisely identifies the lens's shape and the influence of its surfaces on the light that passes through it. The plano surface does not alter the path of light, while the convex surface converges light rays towards a focal point, creating a positive power in the lens.

In contrast, other terms like "biconvex" refer to a lens with two outward-curving surfaces, which is not applicable here as only one surface is curved. The term "plano" alone would imply a lens that could either be plano one side or both sides without any curvature, while "planoconcave" describes a lens with one flat and one inward-curving surface, leading to divergent light rays. Thus, the combination of one flat and one convex surface results specifically in a planoconvex lens.