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

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

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

When an object is placed at a distance of 15 cm from a convex lens, a real image is formed at a distance of 30 cm. What is the focal length of the lens?