Lens formula: What Is Lens Formula

What Is Lens Formula ? Convex lenses are also known as converging lenses since the rays converge after falling on the convex lens , while concave lenses are known as diverging lenses as the rays diverge after falling on the concave lens . Images formed by these lenses can be real or virtual depending on their position from the lens and can have different sizes too. The image distance can be calculated with the knowledge of object distance and focal length with the help of the lens formula . In ... In optics, the relationship between the distance of the image (v), the distance of the object (u), and the focal length (f) of the lens is given by the formula known as the Lens formula . For a treatment using waves and the curvature of the lens surface see Lenses and waves) Two proofs of the formula will be given here, one a geometrical proof and the other an optical version. (a) Geometrical proof of the lens formula Consider a plano-convex lens , as shown in Figure 1. The Lens Formula relates the object distance (u), image distance (v), and focal length (f) of a lens : 1/v - 1/u = 1/f. In CBSE Physics exams, students are often asked to use this formula to calculate the position of an image formed by a convex or concave lens , typically providing two out of the three variables. Careful attention must be paid to sign conventions while applying this formula during calculations.