Question

what is focal power of a spherical mirror or a lens? what may be the reason for using p=1/f as it's expression?​

Answer 1

Answer:

Focal power:It is defined as the reciprocal of focal length of spherical mirror or lens.

Explanation:

Focal power:It is defined as the reciprocal of focal length of spherical mirror or lens.

Or

Focal power is  the degree  of a spherical mirror or lens to which a lens or spherical mirror converge or diverge.

Power of spherical mirror or lens measured in Diopter(D).

Power of lens or spherical mirror can be negative or positive depend upon the type of mirror or lens.

It depends upon focal length .It is inversely proportional  to focal length .If Power is small then focal length is large and focal length is small then power is large.

Therefore, we take power=$\frac{1}{f}$

Where f=focal length (in m)