Question

focal length of a concave mirror is f. in terms of f the separation between an object and its doubly magnified real image by this mirror is​

Answer 1

Answer

focal lenght of concave mirror is f

magnification(M)=2 (real is image)

i.e v/u=2

∴v=2u.........................(1)

using mirror formula

1/f=1/u+1/v

1/f=1/u+1/2u (∵v=2u)

∵f=2u/3............................(2)

Also,

∵u=3f/2................................(3)

From (1) ,we get

∵v=3f (using (3) )

The separation between object and its doubly magnified real = v-u

i.e 3f-3f/2=3f/2 cm