It can also be used to calculate image distance for both real and virtual images. Physics Grade XI Reference Note: Mirror formula for concave mirror when real image is formed and for convex mirror. Move the point named " Focus' " to the right side of the lens to change to a concave lens. If the equation provides a negative image distance, then the image formed is virtual and on the same side as the object. 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 Physics Grade 11 Notes: Lens Formula for Concave Lens. A lens will be converging with positive focal length, and diverging if the focal length is negative. Determine the focal length of the lens. A concave lens is thinner in the middle than it is at the edges. The formula is used to construct lenses with desired focal lengths. The lens formula is applicable to both types of lenses - convex and concave. Here, x 1 and x 2 are the distances to the object and image respectively from the focal points. The formula is applicable to both types of lenses. Learn lens makers formula. Move the point named " Focus' " to change the focal length. 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. Concave lenses. 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. Generally, lenses can be classified as converging (convex) and diverging lenses (concave). Move the tip of the "Object" arrow to move the object. However, if the equation provides a negative focal length, then the lens is a diverging, not converging. Lens Equation Problems and Solutions. This causes parallel rays to diverge. Assumptions and Sign conventions A lens is said to be thin if the gap between the two surfaces is very small. So we can conclude that a convex lens need not necessarily be a converging and a concave lens diverging. Lens maker’s formula relates the focal length, radii of curvature of the curved surfaces, and the refractive index of the transparent material. An expression showing the relation between object distance, image distance and focal length of a mirror is called mirror formula. Figure shows a graph of v against u. Simulation of image formation in concave and convex lenses. The power for a convex lens is positive and the power for a concave lens is negative.