3)Aperture of lens should be small. Lens Formula Derivation. 2. Let the refractive indices of the surrounding medium and the lens material be n1 and n2 respectively. Applicable for both the convex and concave lenses, the lens formula is given as: 1/v - 1/u = 1/f Where, v = Distance of image formed from the optical center of the lens. f = focal length of the lens. u = Distance of object from the optical center of the lens. 2)Object should be a point object. Basic assumptions used in deviation of lens maker formula are as follow: 1)The lens should be thin so that distances measured from its surface may be taken equal to those measured from optical centre . We assume a thin, converging lens and that the light rays we are dealing with are close to the principal axis and make very small angles with the principal axis ( angles of less than 10 o), resulting in very small angles of incidence. 1.Let R 1 and R 2 be the radii of curvature of two spherical surfaces ACB and ADB respectively and P be the … Lens makers formula: It is a relation between the focal length of a lens to the refractive index of its material and the radii of curvature of its two surfaces. 2 placed in a medium of refractive index ? Similarly a concave lens can be made convergent. u = Distance of object from the optical center of the lens. Tags: Class 10 , Physics , Light Reflection Refraction Asked by Rah 1 Answers. Convex Lens Lens maker s formula and lens formula . Let us consider the thin lens with 2 refracting surfaces having the radii of curvatures R1 and R2 respectively. The ray diagram is as follows: Note: The lens maker's formula indicates that a convex lens can behave like a diverging one if m 1 > m 2 i.e., if the lens is placed in a medium whose m is greater than the m of lens. Derivation of Lensmaker’s formula. Lens Formula Derivation Convex Lens ... Derivation. Let us consider a thin lens made up of a medium of refractive index ? f = focal length of the lens. Here is a deriation for lens makers formula: Assumptions. Applicable for both the convex and concave lenses, the lens formula is given as: 1/v - 1/u = 1/f Where, v = Distance of image formed from the optical center of the lens. Derivation for lens makers formula . Derivation The lens maker's formula can be derived for a concave lens in the same way. Such rays are called paraxial rays. 1.