(i) Draw a ray diagram to show the formation of image by a convex lens when an object is placed in fron of the lens between its optical centre and principal focus. (ii) In the above ray diagram markthe object distance (u) and the image distance (v) with their proper signs (+ve or -ve as per the new Cartesian sign convention) and state howthese distances are related to the focal length (f) of the convex lens in this case. (iii) Find the power of a convex lens which forms areal, andinverted image of magnification -1 of an object placed at distance of 20 cm from its optical centre.

(i) Draw a ray diagram to show the formation of image by a convex lens

1.	(i) Draw a ray diagram to show the formation of image by a convex lens when an object is placed in fron of the lens between its optical centre and principal focus. (ii) In the above ray diagram markthe object distance (u) and the image distance (v) with their proper signs (+ve or -ve as per the new Cartesian sign convention) and state howthese distances are related to the focal length (f) of the convex lens in this case. (iii) Find the power of a convex lens which forms areal, andinverted image of magnification -1 of an object placed at distance of 20 cm from its optical centre.
Answer» Solution : (II) Relation: `1/f=1/v-1/U` (III) `m=-1, u=-20cm, v=?,f=?` Marketing of u and v `v=+20cm` Thus object is at 2F i.e. `2f=20 cm` `:.f=10cm =0.1 m` `p=1/f=1/0.1+10D`