Power Of Lens And Mirror - Practice Questions & MCQ

Power and lens and mirror-

Power of a lens is defined as the reciprocal of focal length and Power of a mirror is defined as the negative of reciprocal of focal length.

                                                        So, 

                                                                                  Where, f = focal length

The unit of power is Diopter, 1D = 1 m^-1

The sign of the focal length will be taken according to the sign convention which we have discussed in the previous concept. 

The power of a combination of lenses in contact is the algebraic sum of the powers of individual lenses, so it can be written as -