Lenses Activity

Activity 3

Lenses

Introduction

We use lenses everyday whether we know it or not. There are two lenses in each of our eyes: the cornea and the crystalline lens which focus light onto our corneas. Lenses are used to not only correct our vision, but to enhance it by letting us see worlds we normally wouldn't be able to see, via microscopes and telescopes.

In this Activity, we will explore lenses and their properties by finding the focal lengths and magnifications of various lenses.

Procedure

If you have a printer available, make a print-out of this page by clicking
on the button bar at the top of your browser.
Use one of the lenses in your Optics Kit to look at something up close. Look at the object with each lens separately. Which one of the lenses doesn't seem to magnify objects?
Holding the lens parallel to a tabletop, find the distance from each lens to a sheet of paper upon which a distant light source comes into focus (a ceiling light is probably good enough). This distance is called the focal length of the lens.
On the print-out of this page, measure the length of the arrow below from tip to tail with a centimeter-scale ruler.

Now look through either lens A or lens B at the arrow. Move the lens further or closer to the paper until the image is larger, but at a comfortable viewing distance. Draw the arrow image as you see it in the space below.
Measure the length of the "image" arrow you drew above.
Divide the image length by the length of the real arrow. This number is the magnification of the lens.
Repeat steps 3-6 for the other convex lens in your Kit.

What do you notice about the magnification of each lens and its corresponding focal length? Is there a correlation between the two measurements?

If you came from the Fresnel Lens Activity, Go Back to it now.

To read about Refraction and Why Light Bends, go to the Refraction Readings

To read more about Lenses, Focal Lengths, and Magnification, go to the Lenses Reading