Working with Lenses lab- Abigail Goertzen and Avery Casey

In this lab, we used lenses of various shapes and sizes to find the foci and orientation of each. We also used these lenses to build simple telescopes. Based on the varying styles of the lenses, the resulting foci and orientation were different and therefore recorded.

A) First we set up our equipment, while deterring where the light source was coming from. This happened to be a lightbulb that was across the lab room. Our equipment included a meter stick, several lenses, and a mirror.
B) Then, we found the focal lengths.
a. We then separated the concave lenses and mirrors. We were given one concave lens, 1 large convex lens, one small convex lens, one normal (Flat) lens, one deeply concaved mirror and one slightly concaved mirror.
b. We then began using our light source. We started with the largest diameter convex lens, and formed an image on a note card. In order to find the focal point, we measured the distance from the notecard to the lens in centimeters. We also measured the size of the image (in millimeters) and orientation of the image. The orientation is whether or not the image created on the notecard is right side up or upside down. We repeated this with all convex lenses. Because this cannot be done with concave lenses, we moved on.

c. We then determined and recorded the focal length, image size, and brightness of the image in the mirror. The lens that the mirror's image most resembled was the large convex lens's image. These were the results:

First number is focal length, second is image size, third is image orientation, and fourth is brightness.
1. Concave Lens     Cannot be determined          
3. Convex big lens                       50cm            4mm             Inverted            bright
4. Convex small lens                   6 cm            1mm             Inverted             bright
5. normal lens                             420 cm          3mm            Inverted             brighter
6. Deeply concaved mirror        64


cm            3mm             Inverted             brighter
6. Slightly concaved mirror        64 cm            4mm             inverted             brighter

C) Next, we used the lenses to create simple telescopes.
Astronomical Refractor
a. To create this telescope, we mounted the convex lens which had the longest focal length at the front of the tub as the objective. Then we placed another convex lens as the eyepiece. In order to make the image be in focus, it was necessary to separate the tubes in order to see objects across the room clearly.
b. The equation for the magnification of a telescope is M=fO/fE. We calculated the magnification of the telescope from part a, and then compared them to how much we had estimated they looked bigger. These were the results:
fO (orientation)- Big Convex
fE- little convex
orientation- inverted
estimated amount bigger- 2x
calculated amount bigger- 7.7x

Galilean Refractor
a. For this telescope, we used the concave lens as an eyepiece in the telescope with the same lens from the astronomical refractor. There wasn't a need to separate the tubes out as far for the first telescope in order to find the focus.
b. Next it was time to observe various objects around the room. These were the results:
fO-Big
fE- little (concave)
orientation-not inverted
estimated amount bigger- 5x

In conclusion, it is quite simple to find the focal point of lenses and mirrors with only a few simple items. While learning about the way lenses work, we also learn about the way digital cameras and even our eyes form pictures for us to see.