Between which two points related to a concave mirror should an object be placed to obtain on a screen an image twice the size of the object.
Here by mirror equation we have
1/v + 1/u = 1/f
Let the object needs to be placed at a distance x from the pole
Again we need m = -v/u = 2 because image must be formed having twice the height of the object.
x = -u
v/x = 2
=> x = v/2
1/v + 1/u = 1/f
Thus
1/v + 1/x = 1/f
=> 1/v + 2/v = 1/f
=> v = 3f
x = v/2
=> x = 3f/2
=> x = 1.5f
This means f<x < 2f
=> f<x<r
So image must be placed between F and C