The power of lens is $+5 \mathrm{D}$, then the focal length of the lens will be .

How can you identify a plane, concave and convex mirror by observing image formation?

Establish the relation between the radius of curvature $R$ and focal length $f$ of the spherical concave mirror.

If a mirror forms erect image for objects placed between pole and focus, and it forms real-inverted image for object placed anywhere between focus and infinity, then the mirror is:

Write any three differences between plane and convex mirror.

The unit of power of lens is _____.