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

Solution:-

• Height of the object (ho)= 6 cm

• Focal length(f) = - 20 cm

• Object distance(u) = - 30 cm ( Always measured from the optical center )

By using lens formula ,

➽ 1 / f =  1 / v - 1 / u

On rearranging ,

➽ 1 / v = 1 / f - 1 / u

➽ 1 / v = 1 / - 20 + 1 / 30

➽ 1 / v = - 3 + 2 / 60

➽ 1 / v = - 1 / 60

➽ v = -  60 cm

The image is formed at a distance of 60 cm from the optical center on the same side as that of the object

We know that ,

➽ m = v / u = hi / ho

➽ hi = v x ho / u

➽ hi = - 60 x 6 / - 30

➽ hi = 12 cm

The image formed is enlarged , erect  and virtual