Objective: The purpose of this experiment
is to study the properties of lenses. Student will be provided with a
converging lens; they need to adjust the distance between the light source and
the lens and study the images formed by the lenses at different distance. The
focal length of the lens is determined by placing an object in an infinite
position, the point where the image formed is the focal point. The object this
time can be a sun. The focal length of the lens is determined to be 15.5cm.
Then, students has to put the object, the V shaped filament, in specific
position as required by the lab manual; they have to find the sharp image and
record the observation.
Figure 1: The image formed is inverted.
Figure 2: light from the object passes through the lens.
Materials:
Figure 2: light from the object passes through the lens.
Materials:
Socket lamp with V-shaped filament
Large converging lens
Large split lens or masking tape
Lens holder for large lens
cardboard
Meter stick
Data and Analysis
Focal length (f) = 15.5 ± 0. 5 cm
Table 1: Recorded data of the object and
image distances and heights
Object distance as a multiple of f(cm)
|
Object distance(cm)
|
Image distance(cm)
|
Object height(cm)
|
Image height(cm)
|
M
|
Type of image
|
5f
|
77.5 ± 0.5
|
28.70 ± 0.5
|
8.50 ± 0.2
|
3. 0 ± 0.5
|
0.35
|
Diminished, Inverted, real
|
4f
|
62.0.0 ± 1.00
|
28.5 ± 0.5
|
4.20 ± 0.2
|
0.494
|
Diminished, Inverted, real
|
|
3f
|
46.5 ± 0. 5
|
34 ± 0.5
|
6.40 ± 0.5
|
0.75
|
Diminished, Inverted, real
|
|
2f
|
31.0 ± 0.20
|
51.70 ± 0.2
|
14.50 ± 1
|
1.71
|
Same size, Inverted, real
|
|
1.5f
|
23.0 ± 0.5
|
96 ± 2
|
38.2 ± 2
|
4.49
|
Magnified, Inverted, real
|
Conclusion:
In this experiment, only converging lens,
convex lens is used. From the experiment, student can conclude that the image
formed by convex lens when the object is placed after the focal point is always
inverted and real. When the object is placed further than 2F, the image formed
is diminished. When the object is placed at the 2F, the image formed has the
same size as object. When the object is placed before the 2F, the image formed
is magnified. Since the convex lens is known as converging lens, the light ray
drew on the ray diagram should be converge to a point. To determine the focal
point, an object from infinite point is chosen. The rays from the infinite
object come parallel and form an image at the focal point. When part of the
lens is covered with tape, the whole image can still be seen, but it is much
dimmer. This shows that an image can still be formed even though the light
intensity is much lower. Light ray can pass through only part of the lens to
form an image. When the object is placed at 0.5F, the image formed becomes
virtual, magnified, and erect. It can only be seen inside the lens but not on
the white board because the image is formed on the object side instead of the
opposite side of the lens. This is same with concave lens, which the image is virtual,
diminished, and erect. The image is formed on the object side too and cannot be
seen on the white board.
