Concave lens – Principal focal point (two of them)
Light Rays Through Plano-concave Lens Photograph by Science Stock Photography - Pixels
Refraction of light through concave and convex lenses video - YouTube
Ray Diagrams (3 of 4) Concave and Convex Lenses and Mirrors: Parallel Light Rays - YouTube
Lesson Explainer: Drawing Ray Diagrams for Concave Lenses | Nagwa
Concave - Focuses the lines of light towards a center Convex - Spreads the lines of light Straight - Reflects almost exact | Curved mirror, Reflection, Concave