Question

when an object is placed at a distance of 40 cm from a concave spherical mirror the magnification produced is 1 by 2 where should the object be placed to get a magnification of 1 by 3

Answer 1

u=40 cm

m=1/2=-v/u

1/2=-v/40

v=-20 cm

For getting mangnification 1/3,then

1/3=-20/U

U=-60 cm

Answer 2

m=-v/u
1/2=-v/40
v=20
and using mirror formula we can find the focal length of the mirror
in case two the v and u changes so we can get a different m but the f remains same as we r using the same mirror so let f be x
m=v/u
v=mu
substitute v=mu in the mirror formula and the f value and u will get the u value
i can only show u the path its u who have to walk on it
i hope u will be able to solve it
tq