Physics 102
The Telescope and the Microscope
Juan Guerrero, Phuc La
May 1, 2006
Abstract
The purpose of this lab is to build a microscope and a telescope. It is also to see
the effects of a microscope and telescope.
Data
The focal lengths of all lenses
B lens
cm
15.00
C lens
cm
50.00
D lens
cm
6.00
Microscope
P
Cm
8.00
fB
cm
15.00
fD
cm
6.00
L
cm
37.00
Telescope
fB
cm
15.00
fc
cm
50.00
L
cm
61.00
m
3.5
Graphs
Diagrams are in attached papers.
Calculations
The magnification of the microscope
The microscope helps to clearly see details of a small object. The focal length of
the objective (lens D) is 6.00 cm. The focal length of the eyepiece (lens B) is 15
cm and the distance between two lens is 37.00 cm. The formula below is used to
calculate the magnification of the microscope.
37.00 cm 25 cm
L 25 cm
m
(
)
(
)   10
fD
fB
6.00 cm 15.00 cm
The image is eighteen times larger than the object and the negative shows that
the image is upside down.
The magnification of the telescope
The telescope helps to clearly see objects that are far away. With a telescope a
person can see things that are far away with detail. The focal length of the
objective (lens C) is 50.00 cm. The focal length of the eyepiece (lens B) is 15.00
cm and the distance between the two lens is 61.00 cm. The formula below is
used to calculate the theoretical magnification of the microscope.
fc 50.00 cm
m theo 

 3.333
f B 15.00 cm
The image is four times larger than the object when it is seen without the
telescope from the same distance. The image is also inverted.
In the experiment, the magnification of the telescope is 3.5 times bigger than the
object when it is seen without the telescope. The percent difference between
theoretical and experimental magnification is
| 3.500  3.333 |
% diff 
*100%  4.888 %
3.500  3.333
2
Results
Microscope
p
cm
8.00
fB
cm
15.00
fD
cm
6.00
L
cm
37.00
m
10
Telescope
fB
cm
15.00
fc
cm
50.00
L
cm
61.00
mexp
mtheo
% diff
3.500
3.333
4.888
% Difference
In the experiment, the magnification of the telescope has a theoretical and an
experimental magnification. So, the percent difference can be calculated.
mexp
mtheo
% diff
3.500
3.333
4.888
Questions
1. The magnification of a telescope is the ratio of the objective's focal length
over the eyepiece's focal length. These rays emerge as a parallel bundle
from the ocular. The emergent bundle is inclined to the axis by some
angle different from the entrance angle. Since in this situation all images
are at infinity, image sizes are not accessible to measure. That is why the
telescope magnification is expressed as angular magnification.
2. Although prism binoculars contain converging lenses only, objects viewed
with them are seen erect. The image produced by a telescope may be
inverted by placing a positive lens between the objective and the
eyepiece. When this is done with the astronomical telescope, the normally
inverted image is made erect again. The inverting lens inverts the image
without changing the telescope's magnification much.
3. Two lenses are directly next to each other. The distance from the object to
the objective is p1 and the distance from the image to the object is q1. The
objective has the focal length (f0).
1 1 1
 
f 0 p1 q1
The distance from the image to the eyepiece is p2 and the distance from
the new image to the eyepiece is q2. The eyepiece has the focal length (fe)
1
1
1


f e p2 q2
The distance between the objective and the eyepiece is L. So the second
equation becomes the equation below.
1
1
1


f e L  q1 q 2
Two lens are directly next to each other, so L is assumed to be 0. The
above equation becomes
1
1
1
1
1
1
1

 
 

f e L  q1 q 2 0  q1 q 2  q1 q 2
Two equations are added together to have new equation.
1 1 1
 
f 0 p1 q1
1
1
1


f e  q1 q 2
1 1
1
1
1
1
1
1
 
 
 

f e f 0  q1 q 2 p1 q1
p1 q 2
The distance from the object to the objective is p1. The distance from the
second image to the eyepiece is q2. Two lenses are assumed to be one
lens. p1 becomes p and q2 becomes q. The focal length of new lens is
1 1 1 1 1 1 1
 
   
fe f0 p1 q2 p q f
The equation shows the relationship between two lens and the new lens.
1 1 1
 
f fe f0
Conclusions
In the experiment, the microscope helps to see small objects in detail. It creates
an image that is much larger then the actual object. The telescope helps to see
objects that are far away. The telescope creates an image of the object that looks
much larger than what the object would look like with the naked eye.
grade: 90/100