Question

an object with the height of 6 cm is placed in the front of concave lens of focal length 20 cm is placed at a distance of 30cm find nature size and position the image and also draw the diagram


​

Answer 1

Here,

Image distance=v=20cm,

Object distance=u=−30cm,

Lens equation is given by,

v

1

​  

−  

u

1

​  

=  

f

1

​  

,

putting the values we get,

20

1

​  

−  

−30

1

​  

=  

f

1

​  

,

∴f=12cm

∴ Focal length of convex lens=f=12cm