By opthalmology there are two types of spectacle lenses.SPHERICAL CYLINDERICAL. Charecteristics of these pl

Question

According to opthalmology there are two types of spectacle lenses.SPHERICAL and CYLINDERICAL. let me know the charecteristiuc sof thse lenses. When we placed the spericl lens under a source of light its obtained image is CIRCLE without change in AXIS i.e 180. When we placed the Cylinderical lens under a source of light its obtained image is ELLIPSE with chang ein axis. How to get a stable POWER of THE CYLINDERICAL GLASS wit change in axis?

Answer 1

Since a true cylindrical lens will show no magnification along its length, you measure the magnification and therefore the power across the axis. You don't rotate it while you are measuring it.