Question

We are given a convex lens of focal length 20cm .Draw a ray diagram to show the nature, size and position of the image formed when the object is kept at a distance of 55 cm,35 cmand 15 cm from the lens.

Answer 1

Given focal length of the lens is f= 20cm   so 2f =40cm

Case1   When the object is kept at a distance of 55cm from the lens the object is placed beyond 2f

so the image is formed between f and 2f and the nature of the image  is real inverted and diminished.

Case2    When the object is kept at a distance of 35cmfrom the lens then the object is between  f and 2f

So the image is formed beyond 2f and the nature of the image is real inverted and enlarged.

Case3 When the object is placed at a distance of 15cm from the lens then the object is placed between the optical center and f.

so the nature of the image is virtual erect and enlarged.

Answer 2

Answer:

Explanation:It is not easy to make 20,40,55 cm so I have divided it by 10 and if f is 20 cm so 2f will be 2×2=4cm