For most people, the nearest distance that objects can be located away from the eye and still seen clearly is . This is referred to as the near point; if the object comes any closer, the object cannot be seen clearly. Suppose that a person who needs glasses cannot see objects clearly if they are closer than from the eye; that is to say, their near point is . A lens with what refractive power is needed in order to correct this person's vision to bring their near point to ?

An object located away from a convex lens whose focal point is produces an image located at what distance away from the lens?

A convex lens connected to a projector projects an image onto a board of an object that is away from the lens. If the object is tall and the inverted image is tall, what is the focal length of the projector lens?