Converging
Lenses
Isaac Ilivicky and Noam Kantor
Purpose
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The purpose of this lab was to investigate the
relationship between the object distance and the image
distance for real images produced by a converging thin
lens. In order to do this, we specifically analyzed the
relationships between:
Image Distance vs. Object Distance
Image Height vs. Object distance
Hypothesis
• As the object distance increases, the image
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distance decreases.
As the object distance increases, the image
height decreases.
Apparatus
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A converging thin lens
Multiple rails preferably with an attached scale (meter sticks on the sides)
A light source (light bulb)
The Object (an opaque sheet with a symbol of some sort cut out in the
center, ours happened to be an “L”)
A screen where the image will be shown (multiple sizes will most likely be
necessary)
A computer with LoggerPro or an organized data table of some sort
Time, patience, and some humor
Procedure
1.
Measure the focal length by pointing lens at an object very far away. The prime object in our physics explorations
has been a power pole across the highway. Adjust the position of the screen until the object is very “in focus.”
The distance from the lens to the screen is the focal length of the lens.
2.
In a dark laboratory, start with the object 15 focal lengths away form the lens. On the opposite side of the lens
from the object, move the screen until you find a well-focused image. Record the distance from the lens is known
as the object distance.
3.
Change the object distance in increments of approximately one focal length (rounded to the nearest 5.0 cm) until
you reach a distance of 3 focal lengths away from the lens, recording the image distance and image height each
time. Our suggestion is that in order to measure the same values without having to move the object every time
(which with our apparatus was part of the light source), it is easier to move the lens and the screen.
4.
5.
When you are 3 focal lengths away from the lens, reduce the distance increment to 5.0 cm.
6.
Another reminder; at every position, remember to record the object distance, image distance, and the image
height.
7.
Plot image distance vs. object distance and image height vs. object distance, and proceed with the analysis.
When you are 2 focal lengths away, reduce the distance increment to 1.0 cm until you reach an object distance of
1.0 cm less than 1 focal length away.
Diagram
Credit to the UCLA physics department, however, due
to current situations, GO TROJANS!
Raw Data
Raw Graph
Image Distance vs. Object Distance
Manipulated Graph
Linearized Graph
Mathematical Analysis
Image Distance vs. Object Distance
Raw Graph
Manipulated Graph
Linearized Graph
Mathematical Analysis
Image Distance vs. Object Distance
Error Sources
It was exceedingly difficult to tell whether an
image was focused at a given position when
the image distance was large because the
image was dim anyways. So it was hard to
differentiate between dimness and being out
of focus.
Error Values
Experiment 1:
7.9%
Experiment 2:
7.9%
Ray Diagram!
Error Sources
The scale for the height only went to the
nearest 2mm, so there was a large amount of
estimation. At large object distances, the
image was very small, and so this small scale
was difficult to read.
Mathematical Model
Optics – Converging Lenses
Noam Kantor and Isaac Ilivicky
Experiment 1:
Experiment 2:
Geometric Model
http://www.physicsclassroom.com/Class/refrn/u14l5da5
.gif