Question

28. A 4cm tall object placed perpendicular the principal axis of a concave lens of focal length
15cm. The distance of the object from the lens is 20cm. Find Nature, Position and size of the
image. Also find Magnification.
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Answer 1

Answer:

I think you can understand this

Explanation:

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+f

uf

=

−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/u=−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 .