Lenses (Converging)

Objective
Use thin a lenses to verify the equation 1/p + 1/q =1/f

Procedure

Observe and measure the focal length by putting the lenses under the sunshine.

Set up the equipments: put the lenses on a ruler and project the light through the lenses on a piece of 

paper

The image on the paper (when focus)

measure the distance from the light source to the lenses (p), and from the lenses to the image (q)

Data

Data Analysis

Since 1/p + 1/ q = 1/ f

1/p = -1/q + 1/f
if we graph 1/p vs 1/q, the slope should be about 1, and the x intersection should be 1/f.

Graph

From the graph, we calculate that f=1/0.1653=6.05 cm. And the focal length we measured in the beginning of the lab is 5.85. The percent error is 3.42%.

Conclusion

We are surprised that the error is only about 3% because when we measured the focal length by eyes, it seemed to have a big error. In this lab, we observed that when the object distance is more greater than f, the imagines are always inverted and smaller than the object. However, when the object distance is smaller than the focal length, we can see upright images and they are larger than the objective. We also verified the equation 1/p +1/q =1/f