In his workshop in Padua, Italy, he discovered that plano-convex and plano-concave lenses worked ... beyond which enlarging the image made what was seen through the telescope too small to be ...

In a ray diagram, a concave lens is drawn as a vertical line with inward facing arrows to indicate the shape of the lens.

Draw a ray which passes from the object through the centre of the lens. Some ray diagrams may also show a third ray. Peep holes contain concave lenses. They are set into doors so the occupant can ...