. . Image Formation in Lenses Using Ray Diagrams We can represent image formation by lenses using ray diagrams. Ray diagrams will also help us to study the nature, position and relative size of the image formed by lenses.
For drawing ray diagrams in lenses, alike of spherical mirrors, we consider any two of the following rays – (i) A ray of light from the object, parallel to the principal axis, after refraction from a convex lens, passes through the principal focus on the other side of the lens, as shown in Fig. . (a). In case of a concave lens, the ray appears to diverge from the principal focus located on the same side of the lens, as shown in Fig.
. (b). Table . Nature, position and relative size of the image formed by a concave lens for various positions of the object Position of the Position of Relative size of Nature of object the image the image the image At infinity At focus F Highly diminished, Virtual and erect point-sized Between infinity and Between focus F Diminished Virtual and erect optical centre O and optical centre O of the lens Figure .
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(ii) A ray of light passing through a principal focus, after refraction from a convex lens, will emerge parallel to the principal axis. This is shown in Fig. . (a).
A ray of light appearing to meet at the principal focus of a concave lens, after refraction, will emerge parallel to the principal axis. This is shown in Fig. . (b).
(iii) A ray of light passing through the optical centre of a lens will emerge without any deviation. This is illustrated in Fig. . (a) and Fig.
. (b). The ray diagrams for the image formation in a convex lens for a few positions of the object are shown in Fig. .
. The ray diagrams representing the image formation in a concave lens for various positions of the object are shown in Fig. . .
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Figure . Figure . Figure . The position, size and the nature of the image formed by a convex lens for various positions of the object Figure .
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Nature, position and relative size of the image formed by a concave lens