Suppose a student who was farsighted wears glasses that allows him to read at a distance of from his eyes to the book. His near-point distance is . If his glasses are from his eyes, what is the refractive power of his glasses lenses?

A flower is placed away from a converging lens. An upside down image of the flower is measured as tall and at a distance of from the lens. Find the focal length of the lens and the real height of the flower.

You are passing a ray of light through a thin tank of alcohol to determine properties. Assume that the light ray is not effected by the tank's exterior. You find that if a piece of white paper is put underneath the alcohol tank, there is an image on the metal.

If the top of the image is from the center of the tank, and the top of the object is located from the center of the tank, what is the focal length of this lens?