A person use a spectancle of power of lens - 1.25 D.
Find the focal length of the lens ?

A person use a spectancle of power of lens - 1.25 D. What type of lens is this ?

It is written by the doctor for the eye lens as -2.50. What is the focal length of the lens ?

A virtual image of an object is formed at 30 cm away from a lens when an object is kept at a distance 20 cm away from it . What is the focal length of the lens ? Find the magnification of the image ?

What change occurs for power of a lens when its focal length increases ?