# The linear magnification of a convex mirror of focal length 15 cm is 1/3. What is the distance of the object from the focus of the mirror ?

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The linear magnification of a convex mirror of focal length 15 cm is 1/3. What is the distance of the object from the focus of the mirror ?

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Here, m=1/3,f=15cm,u=?
From m=v/-u=1/3  v = -u/3
From (1)/(v) + 1/u =(1)/(f)
-3/u +1/u =1/15
u = -30cm.
This is the distance of the object from pole of the mirror i.e. PO= -30 cm . Distance of object from focus of mirror OF =OP +PF=30+15 =45 cm