Experiment 10: Lenses

We began this experiment by measuring the focal distance of the lens that were were using. To do this we used the sun as our source and moved the lens until the light was focused at a single point. We then measured the distance from this point to the lens. We determined that the focal distance for our particular lens to be about 19.5 centimeters. We then shined an image through our lens and measured the object distance, image distance, object height, image height, and we calculated the magnification. We also stated whether or not the image was inverted.

Object distance (d_o, cm)	Image distance (d_i, cm)	Object height (h_o, cm)	Image height (h_i, cm)	Magnification	Type of Image
100	26.5	3	0.8	0.266	Inverted
80	28.5	3	1	0.333	Inverted
60	32	3	1.5	0.5	Inverted
40	43.5	3	3.5	1.16	Inverted
30	71	3	6.7	2.23	Inverted

We found that in every case the image was inverted, but when be placed the object within the focal distance no image could be seen. Only when you looked though the lens could you see an image in the lens. To describe the relationship between image distance and object distance we took the inverse of d_i and plotted it against the negative inverse of d_o. We then obtain the following graph.



This graph illustrates that the equation 1/d_o + 1/d_i = 1/f. However this graph shows that the focal length of our lens to actually be 20.9 cm long. This is a percent difference of 6.6% which is in a reasonable percent error when considering the error that went into this experiment. If we wished to decrease the percent error we could have used more accurate measuring equipment and have used a different method when it came to measuring the focal length of our lens.