The size of the real image formed by a convex lens is same with the object. The focal length of the lens is -(a) u/2 (b) 2u (c) 2v (d) v

Let image distance be 'v'
Object distance be 'u'.
According to question
v=u
In convex lens, u=-ve and v=+ve
according to lens formula
1/f=1/v -1/u
= 1/v -1/v
= 1/v -(-1)/v
= 1/v+1/v
1/f=2/v
f. = v/2

I guess the answer is like this
:)

Ok this is the continuation of my previous answer....
Since v=u
We can write it as u/2 as well.....