Lenses Lab

Purpose:
We are going to observe the change in image of an object when the light source ray is passing through a convex-convex lens while changing image distance and object distance (certain number times focal length).

First of all, we hold the lens in a sunshine place and let the parallel light focus at one point on the ground, and we measure the distance between the lens and the focus point on ground to find the focal length.

Trial	Focal Length (cm)	Avg(Focal Length) (cm)	Uncertainties (cm)
1	14.1	14.96666667	-0.866666667
2	15.8		0.833333333
3	15		0.033333333

We find the focal length of lens is 14.967 ± 3.33333 x 10^-10 cm


We vary position of object, lens and screen to get a sharp image.

Object distance (cm)	Image distance (cm)	Object height (cm)	Image height(cm)	M	Type of image
5f=79.88 ± 0.05	23.45 ± 0.05	3 ± 0.05	1.3 ± 0.05	0.43 ± 0.018	Inverted
4f=59.88 ± 0.05	24.5 ± 0.05	3 ± 0.05	1.75 ± 0.05	0.58 ± 0.019	Inverted
3f=39.91 ± 0.05	28.7 ± 0.05	3 ± 0.05	1.95 ± 0.05	0.65 ± 0.020	Inverted
2f=29.99 ± 0.05	44.5 ± 0.05	3 ± 0.05	5.2 ± 0.05	1.73 ± 0.033	Inverted
1.5f=22.96 ± 0.05	332.5 ± 0.05	3 ± 0.05	53.6 ± 0.05	17.87 ± 0.298	Inverted

We plot a graph of inverse image distance vs. negative inverse object distance.

Data:

Inverse image distance (cm)^-1	Negative inverse object distance (cm)^-1
0.042643923	-0.012518778
0.040816327	-0.016700067
0.034843206	-0.025056377
0.02247191	-0.033344448
0.003007519	-0.043554007

Graph:


Slope of the graph is 1.271 which closed to 1.
Y-Intercept means 1/focal length. We have the y-intercept on the graph = 0.062 cm^-1, and we have the focal length on the graph = 16.129 cm. We have the focal length measured = 14.967 ± 3.33333 x 10^-10 cm, so the focal length on graph is in the range of focal length measured.

Conclusion:
We conduct the lens experiment successfully. We successfully observe the change in image of an object through convex-convex lens while changing image distance and object distance. We successful plot the graph and find slope and y-intercept from the graph, and we measure the focal length of lens correctly as the focal length on graph is in the range of focal length measured.