Laboratory Exercise 4
In this laboratory exercise students will build a simple Keplerian
telescope, a simple Galilean telescope, and a compound microscope.
Equipment:
Optical track
50 cm focal length 2'' diameter converging lens
5 cm focal length 1'' diameter converging lens
5 cm focal 1'' diameter length diverging lens
3.8 cm focal length 2'' diameter converging lens
Meter Stick, Ruler
Various viewing targets
Experiment 1: A Keplerian Telescope
Build a Keplerian telescope with a magnifying power of ~10. Use a 2''
lens with a focal length of 50 cm for the objective and a 1'' lens with a
focal length of 5 cm for the eyepiece. Use plano-convex lenses with
one flat side and one curved side. Let the center to center distance
between the lenses be ~55cm and let the flat sides of the lenses face
each other.
Build your telescope on the optical rail. You can easily slide the
components along the rail without destroying the alignment.
Screw the objective to the rail. Place your eye approximately 5
cm away from the eyepiece and move the eyepiece back and
forth until you can see a sharp image of a distant target. Look
at the most distant target you can find considering the size
limitations of the laboratory.
Evaluate the performance of your telescope. Can you see
features of the target through the telescope that you cannot see
when you view the target from the same distance with the naked
eye? Is the image upright or inverted? How does your field of
view (the biggest angle in your view away from the center line
from your eye to the target) change when you switch from
looking at the target with your naked eye to looking through the
telescope?
A Keplerian telescope
Images of targets with a camera replacing the eye
Experiment 2: A Galilean Telescope
Build a Galilean telescope with a magnifying power MP ~10. Use a
plano-convex 2'' lens with a focal length of 50 cm for the objective and
a plano-concave 1'' lens with a focal length of -5cm for the
eyepiece. Let the center to center distance between the lenses be
~45cm and let the flat sides of the lenses face each other.
Build your telescope on the optical rail. Place your eye as close
as possible to the eyepiece and move the eyepiece back and
forth until you can see a sharp image of a distant target. Look
at the most distant target you can find considering the size
limitations of the laboratory.
Evaluate the performance of your telescope. Can you see
features of the target through the telescope that you cannot see
when you view the target from the same distance with the naked
eye? Is the image upright or inverted? How does your field of
view change when you switch from looking at the target with
your naked eye to looking through the telescope? Compare this
telescope with the Keplerian telescope and comment on
advantages and disadvantages.
A Galilean telescope
An image with a camera replacing the eye
Experiment 3: A Compound Microscope
Design a simple compound microscope with a tube length g of 16 cm
and a magnifying power MP ~20. 16 cm is the most common tube
length for laboratory microscopes. Use the 38 cm focal length 2''
converging lens as the objective and the 5 cm focal length 1'' diameter
converging lens as the eyepiece. Let the center to center distance
between the lenses be ~25cm. Place the target ~5 cm in front of the
objective.
Build your microscope on the optical rail. Place your eye as
close as possible to the eyepiece and move the object back and
forth until you can see a sharp image of the object. (If
necessary, adjust the position of the eyepiece.)
Evaluate the performance of your compound microscope.
A compound microscope
An image with a camera replacing the eye
Laboratory 2 Report:
Name:
E-mail address:
In a few words, describe the experiment.
Comment on the procedure. Did you encounter difficulties or
surprises?
Evaluate the performance of your Keplerian telescope, your
Galilean telescope, and your compound microscope.