3B Scientific Optical Bench U, 1200 mm - Manual (Page 16)

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Experiment 9: Concave and convex lenses
9.1 Equipment:
•
Optical bench U17150
•
Experimental lamp U17140
•
Object holder shaft-mounted U17000
•
Diaphragm with fivefold slit from U17040
•
Concave lens f = +150 mm U17108
•
Optical disc U17128
•
Lenses from U17128
•
3 Optical rider 75 mm U17160
•
1 Optical rider 30 mm U17161
•
Plug-in power supply unit U13900
9.2 Set up
•
Place the experimental lamp horizontally on the
rail at the 10 cm position.
•
Set the object holder up with fivefold slit horizon-
tally on the rail at the 22 cm position.
•
Place the concave lens at the 27 cm position.
•
Set up the optical disc with lens on the small opti-
cal rider.
9.3 Procedure
•
Place the convex lens in a central position on the
optical disc.
•
Adjust the height of the disc so that the center of
the incident light beam propagates on the 0° line.
•
A convex lens is a converging lens. After passing
through the medium the light rays all converge at
the focal point F.
•
Repeat the experiment using the concave lens.
•
The light rays diverge after passing through the lens.
No image of an object emerges. Tracing the diver-
gent rays backwards one arrives at a virtual focal
point F' where these lines meet.
Experiment 10: Lens formula and magnification
10.1 Equipment:
•
Optical bench U17150
•
Experimental lamp U17140
•
Object holder, shaft-mounted U17000
•
Slide with letter “F” from U17040
•
Concave lens f = +50 mm U17101
•
Concave lens f = +100 mm U17102
•
Concave lens f = +150 mm U17103
•
Concave lens f = +200 mm U17104
•
Concave lens f = +300 mm U17105
•
Projection screen U17125
•
4 optical rider 75 mm U17160
•
1 optical rider 30 mm U17161
•
Plug-in power supply unit U13900
10.2 Set up
•
Place the experimental lamp vertically on the rail
at the left-hand end.
•
Situate the condensing lens f = +50 mm directly in
front of the lamp.
•
Insert the slide into the holder at the 0 position.
The slot is inserted in the holder so that the letter
“F” is upside down.
•
Place the imaging lens f = +100 at the 12 cm posi-
tion.
•
Set up the projection screen at 100 cm.
10.3 Procedure
•
A sharp image of the slide appears on the projec-
tion screen.
•
The distance between the imaging lens and the
object (slide) is referred to as the object distance v.
•
The distance between the imaging lens and the
projection screen is called the image distance b.
•
In this experiment we have v = 12 cm and b = 88 cm
at a focal length f = +100 mm. Additional values
which result in the production of a sharp image
are:
Object distance Image distance
120 mm 880 mm
130 mm 520 mm
200 mm 200 mm
880 mm 120 mm
•
These distances are determined by the lens formu-
la:
1 1 1
b v f
+ =
•
The magnification can be determined by the ratio
b/v.
•
Perform the experiment with additional lenses
f = +150 mm, +200 mm, +300 mm. At the same
time be sure to move the screen further and fur-
ther away.