Lenses and Mirrors
Lenses and mirrors
Objective
The objective of this experiment is study and understand the characteristics or features of mirrors
and lenses and closely examine the produced images.
Introduction
This laboratory experiment analyzes the physical configurations of mirrors and lenses. The major
experiment components include image screen, the object and optics device which are placed in
such a way that they can be easily repositioned. The components’ positions are determined using
a meter stick. When light from a particular source passes through a lens with the resulting image
being focused on a screen. Both mirrors and lenses have the focal length, f, as a common
characteristic. The focal length is defined to be the distance of the image for an object that is
considered to be infinitely positioned. (Jerry D. Wilson, 2014)
Theory
The geometry analysis of diagrams for mirrors and lenses that provides a mathematical
relationship between the image position (s’), the object position(s) and the focal length(f).
These characteristic quantities are obtained from the lens or mirrors’ surface and the formula is
as shown below:
1/s + 1/s’ = 1/f
3
Lenses and Mirrors
It is worth noting that the above formula is applicable to all thin lenses, mirrors and all image
types. However, in the case of spherical mirrors, the radius of curvature is two times larger than
the focal length. on the other hand, lens or mirror magnification is obtained as follows:
h’/h = s’/s
where h' is the image height and h is the object height.
The figure below demonstrates the experiment:
The figure indicates the distance of the object(p) and the distance of the image (q) both of which
are measured from the lens center. The image height is indicated by h’ while the object height is
h. (Neena Sinha, 2002)
Procedure
The experiment is set up as shown below. The position of the slit plate lens is adjusted such that
a ray parallel to the table is obtained. The experiment is done in three parts as illustrated.
4
Lenses and Mirrors
Results
5
Lenses and Mirrors
Lens
Focal
Length
(cm)
Measured
Distances (cm)
Measured
Heights(cm)
Magnifications
Focal
Length
(cm)
or
DIREC
T
OBJEC
T
IMAG
E
OBJE
CT
IMA
GE
DISTAN
CES
HEIGH
TS
CALCUL
ATED
Mirr
or
fdirect ± o ± i ± O ± I ± m = i/o ±
m =
I/O
± fcalc
A 18 0 23 0.1 # 0.1
3.
4
0.
1
4.
5
0.
1
1760.2
15.
3
18
A
(rev)
77 0.1 # 0.1
3.
4
0.
1
1.
1
0.
1
1797.8
3.7
4
18
B 9.5 0 11 0.1 # 0.1
3.
4
0.
1
2
7
0.
1
1010
91.
8
10
B
(rev)
22 0.1 # 0.1
3.
4
0.
1
0.
7
0.
1
1687.8
2.3
8
17
B+C 24.3 0 33 0.1 # 0.1
3.
4
0.
1
7.
5
0.
1
2193.8
25.
5
22
B+C
(rev)
33 0.1 # 0.1
3.
4
0.
1
1.
8
0.
1
2211
6.1
2
22
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