Question

How far apart are an object and an image formed by a 89-cmcm-focal-length converging lens if the image is 2.75×2.75× larger than the object and is real?

Answer 1

solution-

we know the magnification m=-di/do=hi/ho

where di =image distance

do=object distance

   hi=image height

ho=object height

and given hi=2.75ho

therefore di=-(hi/ho)do=-2.75do

for real image ,image distance is positive, di=2.75do

by lens equation 1/f=1/di+1/do

   1/89cm=1/2.75do+1/do

do=121.36cm

the given image is real therefore the image is located opposite side of the lens or opposite side of the object

now distance between object and image D=do+di=do+2.75do=3.75do=3.75(121.36cm)

   D=455.11cm.................answer