The purpose of this lab is to observe characteristics of
images on the other side of a converging lens.
Method:
We found the focal length of a lens by using the
sun, a ruler and piece of cardboard. The
distance to get a bright dot on the cardboard as the lens faces the sun is the
focal lenth, which was determined to be 4.2cm.
A lamp with a filament of a distinguishable shape projects a image
though the lens to a piece of cardboard..
The Distance for the lens to the filament (d0) and the
distance from the lens to the image(di) was measured. The filament width (h0) and the
image width (hi) were measured.
For objects too big, the width of the center was used. These were used to calculate the
magnification. This process was repeated
for several distance of the focal length.
Data
|
do(cm)
|
di(cm)
|
ho(cm)
|
hi(cm)
|
M
|
Type of
image
|
inverse
di(cm^-1)
|
inverse
-do(cm^-1)
|
|
21
|
6.3
|
8.8
|
3
|
0.34
|
Real
|
0.158730159
|
-0.047619048
|
|
16.8
|
6.9
|
8.8
|
3.5
|
0.39
|
Real
|
0.144927536
|
-0.05952381
|
|
12.6
|
8.9
|
8.8
|
6
|
0.68
|
Real
|
0.112359551
|
-0.079365079
|
|
8.4
|
14.6
|
1.1
|
2.2
|
2
|
Real
|
0.068493151
|
-0.119047619
|
|
6.3
|
34.8
|
1.1
|
5.9
|
5.4
|
Real
|
0.028735632
|
-0.158730159
|
Analysis
When image is displayed on the cardboard it is real and
inverted both vertically and horizontally.
Since the lense is convex on both sides, the image will not change if we
reverse the lens. If you cover half the
lens, the whole image still shows but dimmer and more blurry because any point
on the lens can produce the image. If
you change the object distance to 0.5f you can not see a real image anymore. However, you can see a virtual one in the
lens. The image is upright.
Graph d0 vs.di
Graph negative inverse d0 vs.inverse di
Slope = 1.18 y-intercept = 0.212
The y intercept is the inverse of the focal length.
We proved
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