Lens maker’s formula relates the focal length, radii of curvature of the curved surfaces, and the refractive index of the transparent material. Concave lenses. Determine the focal length of the lens. The lens formula is applicable to both types of lenses - convex and concave. The formula is applicable to both types of lenses. Consider a ray AD parallel to principal axis falling onto a concave lens of focal length f and being diverged by passing through E. The required equation is 1/f = 1/u + 1/v Lens Equation Problems and Solutions. If the equation provides a negative image distance, then the image formed is virtual and on the same side as the object. Here, x 1 and x 2 are the distances to the object and image respectively from the focal points. Assumptions and Sign conventions A lens will be converging with positive focal length, and diverging if the focal length is negative. Move the tip of the "Object" arrow to move the object. A lens is said to be thin if the gap between the two surfaces is very small. Figure shows a graph of v against u. It can also be used to calculate image distance for both real and virtual images. The power for a convex lens is positive and the power for a concave lens is negative. So we can conclude that a convex lens need not necessarily be a converging and a concave lens diverging. Solution: From the graph, when v = u, the coordinate of the point of intersection is given as (2f, 2f), where f is the focal length of the lens. Learn lens makers formula. The formula is used to construct lenses with desired focal lengths. Physics Grade XI Reference Note: Mirror formula for concave mirror when real image is formed and for convex mirror. Simulation of image formation in concave and convex lenses. Move the point named " Focus' " to the right side of the lens to change to a concave lens. However, if the equation provides a negative focal length, then the lens is a diverging, not converging. An expression showing the relation between object distance, image distance and focal length of a mirror is called mirror formula. This causes parallel rays to diverge. The Newtonian Lens Equation We have been using the “Gaussian Lens Formula” An alternate lens formula is known as the Newtonian Lens Formula which can be easily verified by substituting p = f + x 1 and q = f + x 2 into the Gaussian Lens Formula. Move the point named " Focus' " to change the focal length. Physics Grade 11 Notes: Lens Formula for Concave Lens. Generally, lenses can be classified as converging (convex) and diverging lenses (concave). A concave lens is thinner in the middle than it is at the edges.