Applications

Object at infinity → parallel sunlight converges to F₂.

Object beyond 2F₁ — real, inverted, diminished image at the sensor.

Object at 2F₁ — image is the same size, real and inverted at 2F₂.

Object between 2F₁ and F₁ — real, inverted, magnified image beyond 2F₂.

Object at F₁ — refracted rays emerge parallel; image at infinity.

Object between F₁ and O — virtual, erect, magnified image.

A natural convex lens that adjusts focal length to form a real image on the retina.

A concave lens diverges incoming light so distant objects can focus on the retina.