Experiment 9: Lenses

Introduction: The purpose of this experiment is to investigate the relationship between object distance, image distance, and the focal length of a lens.

Data:
The focal length of a lens was measured by taking the lens outside, using the sunlight to create an image on an object, and measuring the distance between the lens and the focused image.

Set up of the lab at the initial position, the measured focal point multiplied by 5.

 Our experiment has us move the lens in to points of 5f, 4f, 3f, 2f, and 1.5f.

A focused image.

The image at half the focal length. The image becomes virtual.

If someone were to look through the lens at the object, which is the light, they would see an image that is much larger and oriented upright.

Data from experiment

Graph for data of object distance vs. image distance.

Table of data for inverse object distance and inverse image distance.

Graph of inverse values.

Looking at the graph of the inverse values, we can see that we are given a linear equation (y = mx + b), which we can model closely to the equation:

From here, we observe that our y-intercept on the graph is related to our inverse focal length. 

Focal length from graph = 1/.1098 = 9.11 cm.

Measured focal length = 8 cm. 

% error = (9.11-8)/9.11 * 100 = 12.2%

Our error could come from the fact that it was a cloudy day, so measuring focal length using sunlight was very difficult. Measurements taken could have been off.