Question

a convex mirror foms a real image of height 4 centimetre of an object of height 1 cm placed 20 cm away from the mirror

Answer 1

A convex mirror foms a real image of height 4 centimetre of an object of height 1 cm placed 20 cm away from the mirror.

Himage=4
Hobject=1
u=--20

we know

Magnification is equal to Hi/Ho=4

Magnification=v/u

So v=--80cm

Using mirror formula or use m=f/f-u  or  m=f-v/f

I will use 2nd one

4=f/f+20
4f+80=f
f=--80/3

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