What is meant by power of a lens ? What is one dioptre ?
What is meant by power of a lens ? When is it positive or negative? Define one dioptre.
What is meant by power of a lens? Write its SI unit. A student uses a lens of focal length 40 cm and another of -20 cm. Write the nature and power of each lens.
What is meant by number of lens?
The radii of curvature of both the surfaces of a convex lens are equal. One of the surfaces is made plane by grinding. What is the new focal power of the lens ?