If ‘u’ is the object-distance, ‘v’ is the image-distance and ‘f’ is the focal length of a spherical mirror then which of the following is a correct expression for the mirror formula?

A

$$\frac{1}{v} + \frac{1}{u} = -\frac{1}{f}$$

B

$$\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$$

C

$$\frac{1}{v} + \frac{1}{u} = \frac{1}{f}$$

D

$$\frac{1}{v} - \frac{1}{u} = -\frac{1}{f}$$