diverging lenses

Thicker on the edges than in the center; they cause parallel light rays emanating from an object to diverge.

plano-concave lens

Lens with one flat side and one concave side (curving inward).

concave lens

Lens with one side curving inward; the greater the curvature, the more the light rays diverge.

biconcave lens

Lens with both sides curving inward.

negative meniscus

Lens where the concave side (curving inward) is more pronounced than the convex side (bulging outward).