Question

an object 4 cm high is placed 15 cm from a convex lens of focal length 5 cm.draw a ray diagram and find the position,size and nature of te image

Answer 1

Explanation:

Object distance given is 15cm which is (u).

Object length(o) = 4 cm.

Focal length(f) = 5 cm.

Thus, magnification(m) is object distance / image distance

m=i/o.

Or, we can say -

1/v - 1/u=1/f

1/v - 1/15 = 1/5

So, 1/v = 1/5 + 1/15

        1/v = 4/15

          v= 15/4 cm which is the position of the image from the                 convex lense.

Thus, magnification is (f-v)/f=m

                                 =(5-15/4)/5=m

                                 = 5/20=m

                                  m=1/4.

Now, m=i/o for all lenses  

=1/4=image / 4

So, image distance is 1 cm.

Nature of the image will be larger and inverted.