15.2 Images formed by convex lenses The nature of image formed by a convex lens Can the image be formed on a screen? The image formed is erect and magnified Hold a magnifying glass close to the prints of a book… No. A virtual image is formed.

15.2 Images formed by convex lenses Can the image be formed on a screen? When we use the magnifying glass to form an image of a distant building… The image formed is inverted and diminished. Yes. A real image is formed.

15.2 Images formed by convex lenses Ray diagrams for convex lenses Construction rules for convex lenses F’ F C Rule 1 A ray parallel to the principal axis… …emerges from the lens in a direction that passes through F.

15.2 Images formed by convex lenses Rule 2 A ray passing through F’… F’ F C …emerges parallel to the principal axis

15.2 Images formed by convex lenses Rule 3 A ray passing through optical centre is undeviated. F’ F C

15.2 Images formed by convex lenses  We can locate an image by using any two of the construction rules.  We use a symbol to represent a convex lens:

15.2 Images formed by convex lenses Image formed by a convex lens for various object distance 2F’ 2F2FF F’ parallel rays from a distant object focal plane image object: far away image: at F real, inverted and diminished

15.2 Images formed by convex lenses object: beyond 2F’ image: between F and 2F real, inverted and diminished 2F’ 2F2FF F’ image object

15.2 Images formed by convex lenses object: at 2F’ image: at 2F real, inverted and same size as the object 2F’ 2F2FF F’ image object

15.2 Images formed by convex lenses 2F’ 2F2FF F’ image object object: between 2F’ and F’ image: beyond 2F real, inverted and magnified

15.2 Images formed by convex lenses 2F’ 2F2FF F’ image formed at infinity object object: at F’ image: at infinity

15.2 Images formed by convex lenses 2F’ 2F2FF F’ image object object: within F’ image: on the same side as the object virtual, erect and magnified Simulation: Image formed by convex lens

15.2 Images formed by convex lenses image: real object: within F’ object: beyond F’ image: virtual How can we determine whether the image is real or virtual?

15.2 Images formed by convex lenses How can we determine whether the image is magnified, diminished or same size as the object? image: diminished object: within 2F’ object: beyond 2F’ image: magnified object: at 2F’ image: same size as the object

15.2 Images formed by convex lenses That’s the end of Section 15.2 Check Point Key Ideas Previous Page Section 15.3 Exit