Chapter 25, Problem 9Q

To determine

If reading glasses are magnifiers and to discuss the similarities and differences of converging lenses used for these two purposes.

Answer to Problem 9Q

Solution:

Reading glasses are magnifiers, and both reading glasses and magnifiers are converging lenses.

Explanation of Solution

Both reading glasses and magnifiers are converging lenses.

A magnifier has the following properties

• Generally a short focal length lens.
• Magnifier is used in such a way that the distance between lens and object is adjusted to have the object exactly or just inside the focal point. An object at the focal point will form image at infinity andeasily viewed by relaxed eye. We can adjust the lens to make the image at the near point of the eye and have slightly more magnification.

A reading glasses has the following properties

• Focal length of the reading glass lens depends on the individual eye.
• The lens are at fixed distance from the eye, used when the near point is far away. These lenses have the rays from the nearby object converged before they reach the eye, such that eye can focus on object inside its near point.

Both reading glasses lens and magnifiers lens helps the eye to focus on object closer than the near point of the eye.