Question

an lighted object is at 1m distance from the screen inage has been formed by a convex lens. if the magnification is 3 then find the focal length of the lens.

Answer 1

It can be same fpcal length if u learn physics properly . You don't know how to ask the question. Rascal

Answer 2

m =+3
because it is by convex lens
now u=1m
v/u=m
v/1=3
v=3m
now 1/v-1/u=1/f
1/3+1=1/f
4/3=1/f
3/4=f
f=0.75m