A short linear object of length \[l\] lies along the axis of a concave mirror of focal length f at a distance \[u\] from the pole of the mirror. The size of the image is approximately equal to [IIT-JEE 1988; BHU 2003; CPMT 2004]

• A.            \[l{{\left( \frac{u-f}{f} \right)}^{1/2}}\]                        
• B.            \[l{{\left( \frac{u-f}{f} \right)}^{2}}\]
• C.            \[l{{\left( \frac{f}{u-f} \right)}^{1/2}}\]                        
• D.            \[l{{\left( \frac{f}{u-f} \right)}^{2}}\]