Use mirror equation to show that an object placed between F and 2F of a concave mirror produces a real image beyond 2F.

For a concave mirror, focal length (f) is negative, f

When an object s placed on the left side of the mirror, the object distance (u) is negative, u

 Using lens formula

1/ v  - 1/ u = 1/f

1/v = 1/f -1/u  ......(i)

The object lies between f and 2f

2f

1/2f>1/u>1/f

1/f -1/2f

Using equation (i) we get

1/2f

or, 1/2f

or, 2f>v

-v>-2f

Therefore, the image lies beyond 2f