Question

The image of an onject formed by a lens is of magnification 1 if the distance between the object and its image is 60m, what is the focal length of the lens? If the object is moved 20cm towards the lens, where would the image be formed? State reason and also draw a ray diagram in support your answer

Answer 1

Answer:

It is a convex lens. Object is at 2F , image is also at 2F. The distance of lens from object and image is same. So,object distance( from lens)= image distance(from lens)=60/2= 30 cm .

Focal length=30/2=15 cm

For second case,use lens formula,by using

u=-10 cm f=15 cm ,find the image distance yourself.