Question

A divergent lens has a focal length of 3 cm. At what distance should an object of height 5 cm from the
optical center of the lens be placed so that its image is formed 15 cm away from the lens? Find the nature and
size of the image also
​

Answer 1

Answer:

We know that for a divergent lens both u and f are -ive , from lens equation  

                    v=  

u+f

uf

​  

 , as both u and f are -ive therefore v will be -ive ,

given  f=−30cm,v=−15cm ,

 so      u=  

f−v

fv

​  

=  

−30−(−15)

−30×−15

​  

=−30cm ,

now linear magnification m=I/O=v/u ,

given height of object O=5cm,I=? ,

therefore   I/5=15/30 ,

or               I=5×15/30=2.5cm

Explanation: