Question

Compute the position of the object placed in front of a concave mirror of focal
length ‘f’ so that the image formed is of the same size of the object.

Answer 1

We have,
focal length = f
A/Q,
Image will be of the same size
means,
object distance will be at the center of curvature of that concave mirror.

Answer 2

Position of object infront of concave mirror of focal length f so that image formed is of same size as that of object is at centre of curvature that is 2f.

We know that mirror formula for concave mirror is :---

1/f=1/u+1/v

And magnification =height of image/height of object

m=hi/ho =v/u m=1 so v=u

I/f=1/u+1/v

I/f=1/u+1/u

1/f=2/u

So u=2f

Hence object must be placed at centre of curvature so that image size and object size are same.