Question

16. A convex lens of focal length 20 cm focus. The image
of an object situated at 25 cm from lens. Find position
and magnification of image.​

Answer 1

Answer:Given:u=−10cm               f=20cm        (convex lens)

To find: v and image's nature.

Solution: From lens formula

v

1

​  

−  

u

1

​  

=  

f

1

​  

 

v

1

​  

+  

10

1

​  

=  

20

1

​  

 

v

1

​  

=  

20

−1

​  

 

v=−20cm

And magnification =  

u

v

​  

=2

Hence image formed is virtual, erect and magnified two times.

Explanation: