A point object O is placed at a distance of 30cm from a convex lens of focal length 20cm cut in to two halves each of which is displaced by 0.05cm as shown in figure. Find the positions of the image. IF more than one image is formed, find their number and distance between them.

A point object O is placed at a distance of 30cm from a convex lens of

1.	A point object O is placed at a distance of 30cm from a convex lens of focal length 20cm cut in to two halves each of which is displaced by 0.05cm as shown in figure. Find the positions of the image. IF more than one image is formed, find their number and distance between them.
Answer» Solution : considering each part as SEPARATE lens with u=-30cm and f=20cm from lens FORMULA `1/v-1/u=1/f` we have `1/v-1/(-30)=1/20` i.e., v=60cm . So each part will form a real image of the point object O at m from the lens as shown in figure. As there are two pieces, two IMAGES are FORMED. Now in similar triangles `OI_1L_2 and OL_1L_2` `(I_1I_2)/(L_1L_2)=(OP)/(OQ)=((u+v))/u i..,e I_1I_2=90/30 times (2 times 0.05)=0.3cm` SO the two images formed are 0.3cm APART.