Definition Lens

The lens is a transparent glass that has a curved surface. Curved surfaces can be:
a. Two convex surface (lens bikonveks).
b. Two concave surfaces (lens bikonkaf).
c. One convex and one concave surface (concave-convex lens / convex-concave lens).
d. One convex surface and one flat surface (plan-convex lens).
e. One concave surface and one flat surface (plan-concave lens).

Figure II.14 Lens Types

The second surface of the lens acts as a refracting surface. Different surfaces produce different total refraction effects. Based on the nature of the shadow formation, the lens can generally be divided into two kinds, namely:
a. Convex lens.
b. Concave lens.