Examining
Images Formed
in Converging
Lenses Lab
Akshana Wettewa
11/22/2011
Examining Images Formed in Converging Lenses Lab
By: Akshana Wettewa
Introduction:
In this lab we will be exploring more about converging lenses. A converging lens has 2
refractive sides, and the two surfaces are convex. When Parallel rays touch the surface of a
converging lens the rays refract inward, then at a certain point the rays will meet. Another word
that is used to call a converging lens is a positive lens. A positive lens is one that causes incident
parallel rays to converge at a focal point on the opposite side of the lens.
Purpose:
The purpose of this lab is to determine what are the characteristics and locations of the
images formed when the distance of the object changes.
Dependant Variable  Is the image distance because we can’t change it without changing the
object distance.
Independent Variable  Is the object distance because we can change it.
Hypothesis:
In case 1 when the object is at 3F (7.5cm) the image will be between F and 2F, at 3.8cm.
Also it is the smaller, upside down and is on the other side. In case 2 when the object is at 2F
(5cm) the image will be at 2F (5cm) on the opposite side. The characteristics of the image are it
is the same size and it is upside down. In case 3 when the object is at 1.5F (3.75cm) the image
will be at 8.4cm on the opposite side. The characteristics of this image are it is bigger and it is
upside down. For case 4 when the object is at 0.5F (1.25cm) the image will not appear on the
screen instead it will appear in the lens. The image will be bigger and right side up. Basically
what happens when the distance changes (comes closer) the image will get bigger until a
certain point.
Materials:
 Lens Lab Kit
o Mirror support
o Lens
o 2 stands
o Meter stick
o Candle holder
o Screen
o Screen holder
 Candle
 Matches or lighter (to light candle
Procedure:
Step 1: Set up lens lab kit.
Step 2: Light candle with the matches.
Step 3: Turn off lights and close windows so you can see the image clearer.
Step 4: Case 1: Move the object (candle) 30cm away from the converging lens.
Step 5: Maneuver the screen until a clear picture is shown.
Step 6: Measure the distance of the image if possible.
Step 7: Case 2: Move the object (candle) 20cm away from the converging lens.
Step 8: Repeat steps 5 & 6.
Step 9: Case 3: Move the object (candle) 15cm away from the converging lens.
Step 10: Repeat steps 5 & 6.
Step 11: Case 4: Move the object (candle) 5cm away from the converging lens.
Step 12: Repeat steps 5 & 6.
Step 13: Put materials back in lens lab kit and clean up rest of the materials.
Observations:
Refer to Appendix A.
Analysis:
Summary Statements:
As we moved the object closer and closer it became bigger and bigger until a certain
point. When we reached this point we could no longer see the image on the screen and
therefore we looked into the lens and that is where we saw the image. Also as we moved the
object closer the distance got longer. The images in Case 1, 2 & 3 were all real and inverted. The
image in Case 4 however was upright and virtual.
Sources of Error:
A source of error we made was our accuracy measuring the distances. This could have
affected our results depending on how much we miscalculated. To prevent this from happening
we could have done the experiment a couple of times to get a more accurate distance.
Discussion:
In real life we use converging lenses many times without even knowing it. In fact a
magnifying glass uses a converging lens to magnify things. The converging lens allows it to get
bigger the further you bring the magnifying glass, which is the concept we explored in this
experiment. Also people with hyperopia use converging lenses to correct their vision.
Hyperopia is a condition where you cannot see objects that are close to you. It is corrected
simply by using a converging lens and its ability to make objects that are near bigger therefore
helping the eye see better (figure # 1).
Conclusion:
The hypothesis stated that as the object gets closer the image will appear bigger until a
certain point. The observations showed that the image in fact did get bigger as the object got
closer. Therefore the hypothesis was accepted.
Appendix:
Hyperopia
Without a converging lens
With a converging lens
Figure # 1
Figure #1
References:
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“Hyperopia” U.S. National Library of Medicine. Web. 11.24.11
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002015/
“Imaging with Lenses” Physics
301.Web.11.25.11http://www.mtholyoke.edu/~mpeterso/classes/phys301/geomopti/lenses.ca
“Measurement of Centering Errors” Trioptics. Web.11.23.11
http://www.trioptics.com/knowledgebase/measurement_centering_errors.php
Book: Heath. Robert. “Fundamentals of Physics”.1979