shalini goyal
Last Activity: 14 Years ago
the correct ans is 35 cm....
soln:-.....for lens "A",
its focal length is 10 cm and object is at 20 cm 4m it,so it means obj is at 2f....so image will b 20 cm far apart it.....n u can also find it by d formula,
1/f=1/v-1/u.......where f,v and u are focal length,image distance and object distance from pole,
now (d-20) is the object distance for lens B,
so,1/15=1/*-1/{-(d-20)}.....where * is infinity as given.....
hense,d-20=15
d=35 cm