Question

24. An object of height 4 cm is placed
perpendicular to the principal axis of a
Concave
lens of local length 10 cm. If object is kept
at a distance 20 cm from optical centre,
then find the size of image.​

Answer 1

Answer:

A 4cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 24cm. ... As we can see that the distance of the object from the lens is smaller than the focal length of the lens. This will clear the fact that the image formed is between the focus and the center of curvature.

Answer 2

Given  -    f=+24cm,u=−16cm ,

As ∣u∣(16cm)<∣f∣(24cm) ,it means object lies between F and C , in this position of object the rays from object cannot meet at any point on the other side of lens ,which is also clear from the position of image found below ,

From lens equation  v=u+fuf=−16+24−16×24=−48cm ,

-ive sign shows that image will be formed on the same side of lens , where the object is placed .

Now linear magnification     m=I/O=v/ -48/-16 = +3

or                                        I=3×4=12cm       (given  O=4cm) ,

since m=+ive and m>1 ,therefore image will be virtual ,erect and magnified