Experiment: Lenses

The purpose of this lab was to explore the type of images that are formed at different abject distances and develop a relationship between the object distance and the image distance.

Equipment:
-Optics Bench
-Light
-Object
-Lens and lens holder
-Whiteboard

First we determined the focal length of the lens by using a distant object such as the sun to find a convergance at a focal point. We determined the focal point pf our lens to be 8 cm.

We then set up our apparatus (below) and we varied the position of the object, lens, and the image screen and tabulated the image height, magnification and the type of image that we viewed.

Below is the data:

When we changed the object distance to .5f (4cm) there was no image. This was because at this point it was a virtual image. If you looked through the lens at the object and viewed the image, you could see the image but it was magnified.

We then plotted a graph of the image distance vs the object distance using centimeters.

We then created a new column of data for the inverse image distance and the negative inverse object distance and plotted a graph of the inverse image distance vs the negative inverse distance.

This graph's slope is y=1.027x+.1099. The y-intercept of this graph is the inverse focal length of the lens that we used. Therefore, the theoretical focal length is 9.11 cm.

The percent error for our focal length is: % Error = (9.11-8)/9.11 * 100% = 12.2%.

This percent error could have come from the fact that we used the sun to find the focal length of the lens, but it was a very gloomy day so taking the measurements of the focal length using the sun were not accurate.