sir a convex lens is resting upon a block attached to a vibrating spring if the amplitude of block is a .if an object is placed on the principal axis of lens at a distance 3f from the mean position of block then please find the distance between the extreme ends of image?

dear nehal i am giving u hint for this but solve by yourself ,

wrt to lens , there are two positions of object which are extream positions of this motion of particle ...

let these points are P,Q then

P = 3f+a , Q = 3f-a

now , inage corresponding to P & Q is P₁ , Q₁

apply lens formula for both images & find P₁& Q₁  then

 (P₁-Q₁)  = distance bw two extream ends

ans is {2f²a/4f²-a²}