Physics (including Earth and space sciences geometric optics)
Project description
You must do Activity B (page 5) number 2,3,4 (especially 2,4) without the data from the experiment. Do page 6 (Question section) on number 1a,b,c,d. If you can also do questions in Activity A without the data.
Activity A: Measuring the focal length of a lens
Your goal is to measure the focal length of a converging lens using the lens equation. You’ll also check
the magnification relationship.
The image for t
his experiment is a card with a lett
er F punched out as holes. The object is illuminated
from behind with a light bulb.
1)
Construct the pictured setup using a meterstick
and the lens and screen clips provided. The object
screen should be at the 10 cm mark, the lens at the 30 cm mark.
2) Measure the height of your object (the letter F) and record it in the data table.
3) Adjust the image screen position until the imag
e is as sharp as possible. You’ll probably need to
move
the image screen
back and forth a few times to find the location that gives the sharpest image.
4) Record the following in the data table:
?
Object distance (distance between the object and the lens)
?
Image distance (distance between the lens and the image screen)
?
Image height (height of the image on the screen)
?
Image orientation (upright or inverted)
5) Calculate the observed magnification (image height / object height)
6) Calculate
?
the focal len
gth of the lens using the lens equation
?
the theoretical magnification (
-
s
i
/s
o
)
?
the magnification percent error
7) Repeat steps 3
-
6 for the object distances
given in the table
plus at least 3 others of your choosing
Object Height h
o
= ____________
S
0
(cm)
S
i
(cm)
H
i
(cm)
Orientation
(inverted/upright)
Observed
Magnification
(h
i
/h
o
)
Theoretical
Magnification
(
-
s
i
/s
o
)
Magnification
% error
Calculated
focal length
(cm)
20
25
30
40
50
Average
f
= __________ cm
Accepted
f
= __________ cm
% error = _____________
Calculate the average focal length of the lens from all your trials. Obtain the accepted value from your
instructor and report a percent error for your measurements. Show
your work.
Your goal is to measure the focal length of a converging lens using the lens equation. You’ll also check
the magnification relationship.
The image for t
his experiment is a card with a lett
er F punched out as holes. The object is illuminated
from behind with a light bulb.
1)
Construct the pictured setup using a meterstick
and the lens and screen clips provided. The object
screen should be at the 10 cm mark, the lens at the 30 cm mark.
2) Measure the height of your object (the letter F) and record it in the data table.
3) Adjust the image screen position until the imag
e is as sharp as possible. You’ll probably need to
move
the image screen
back and forth a few times to find the location that gives the sharpest image.
4) Record the following in the data table:
?
Object distance (distance between the object and the lens)
?
Image distance (distance between the lens and the image screen)
?
Image height (height of the image on the screen)
?
Image orientation (upright or inverted)
5) Calculate the observed magnification (image height / object height)
6) Calculate
?
the focal len
gth of the lens using the lens equation
?
the theoretical magnification (
-
s
i
/s
o
)
?
the magnification percent error
7) Repeat steps 3
-
6 for the object distances
given in the table
plus at least 3 others of your choosing
Object Height h
o
= ____________
S
0
(cm)
S
i
(cm)
H
i
(cm)
Orientation
(inverted/upright)
Observed
Magnification
(h
i
/h
o
)
Theoretical
Magnification
(
-
s
i
/s
o
)
Magnification
% error
Calculated
focal length
(cm)
20
25
30
40
50
Average
f
= __________ cm
Accepted
f
= __________ cm
% error = _____________
Calculate the average focal length of the lens from all your trials. Obtain the accepted value from your
instructor and report a percent error for your measurements. Show
your work.
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