Question

The focal length f of a mirror is given by $\frac{1}{f}=\frac{1}{u}+\frac{1}{v}$ where u and v represent object and image distances respectively. The fractional error in 'f' is given by

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

$f=\frac{uv}{u+v},\frac{△f}{f}=\frac{△u}{u}+\frac{△v}{v}+\frac{△(u+v)}{u+v}=\frac{△u}{u}+\frac{△v}{v}+\frac{△u}{u+v}+\frac{△v}{u+v}$