Optics Lab
watch the video and finish the questions.
Video Link: https://www.youtube.com/watch?v=4dLdeupRQMw
you will find measurements in the video
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Lab #1 Thin Lenses and Uncertainties in Measurement Worksheets
Please watch Lab1 Lecture Part I and Lab1 Lecture Part II in D2L before completing the
worksheets.
Part A: Determine the focal length f of a converging lens
Technique 1: Using a lens-mirror combination
Instructions: View the 1st segment of the video, CSEC Physics Virtual Lab (YouTube Video), in
D2L. Use the pause button when necessary so that you can read measurements. Do not use the
measurements given by the video, as they do not give the correct number of significant figures
and do not include uncertainties.
1) In the video, the smallest division of the tape measure is ________________ .
The uncertainty in measurements using this tape measure is _______________.
The focal length of the converging lens is found to be ___________________________.
(Note: Make sure to include the correct number of significant digits in the reported value
AND include the uncertainty in the stated result.)
2) Draw a ray diagram for the lens-mirror combination below. Show that when the object
is of a focal length away from the lens, an inverted image is formed just below the
object and is also of a focal length away from the lens. F1 and F2 are the focal points of
the lens.
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Technique 2: Using the conjugate foci method
Instructions: View the 2nd segment of the video, CSEC Physics Virtual Lab (YouTube Video), in
D2L. Use the pause button when necessary so that you can read measurements. Do not use the
measurements given by the video, as they do not give the correct number of significant figures
and do not include uncertainties.
Data:
Object position
Xo (cm)
Screen position
Xi (cm)
Lens position
T1 (cm)
Lens position
T2 (cm)
Data Analysis:
1) Calculate in the space below the distance between the object and screen, D (cm), and
the distance between the lens positions, d (cm). Also, show calculations of the
uncertainties, D and d.
(Hint: See Lab1 Lecture Part I, slide #9, Propagation of error in calculations, case 1, sum
and difference. For example, D = Xi Xo. So, D is calculated using the equation for the
case of sum and difference: = , = 2()2 + 2
2
.)
2) Calculate in the space below the focal length f using the equation f = (D2 d2)/(4D). Also,
show calculation of the uncertainty, f. (Hint: Since f is a function of D and d, use the
method discussed in Lab1 Lecture Part I, slide #9, Propagation of error in calculations,
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case 3, general functions, = (, ), =
2
()2 +
2
2
. You will need
to take partial derivatives.)
3) Derive equation, f = (D2 d2)/(4D), from the thin-lens equation, 1/o + 1/i = 1/f, where o
and i are the object and image distances, respectively. Use the figure below to help you.
(Hint: As shown in the diagram, o + i = D, independent of which position you refer to.
First, substitute o with o = D i in the thin-lens equation. Second, rearrange terms to
obtain a quadratic equation of i. Next, solve for i to get solutions, i1 and i2. Finally, set i1
i2 = d, rearrange terms and you will be able to derive the equation required.) Show
your derivation in the space below.
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Conclusion:
The focal length of the converging lens is found to be __________________________.
(Note: Make sure to include the correct number of significant digits in the reported value AND
include the uncertainty in the stated result.)
Part B: Determine the focal length f of a diverging lens
Technique: Using a combination of converging and diverging lenses.
Instructions: Use the figure below to complete the data table.
Data:
Position of Diverging Lens
XDL (cm)
Position of Image I1
XI1 (cm)
Position of Image I2
XI2 (cm)
0 45.00 cm 60.00 cm 80.02 cm 128.55 cm
Optical Bench Tape Measure
(Smallest Division = 0.1 cm)
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Data Analysis:
1) Calculate in the space below the object distance o and image distance i of the diverging
lens (DL). Also, show calculations of the uncertainties, o and i.
2) Calculate in the space below the focal length f of the diverging lens (DL) using the thin-
lens equation, 1/o + 1/i = 1/f. Also, show calculations of the uncertainty, f. (Hint: Study
Example 2 in Lab1 Lecture Part I for help.)
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3) Draw a ray diagram for the lens combination below to show the final image formed.
Clearly show all the rays with arrows indicating direction. F1 and F1 are the focal points
of the converging lens (CL), and F2 and F2 are the focal points of the diverging lens (DL).
Conclusion:
The focal length of the diverging lens is found to be __________________________. (Note:
Make sure to include the correct number of significant digits in the reported value AND include
the uncertainty in the stated result.)
