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3. Operation
3.1 Set-up
To perform the experiment the following equip-
ment is also required:
1 optical lamp
1 plug-in power supply unit
1 tube holder D U19100
1 convex lens
1 object holder, shaft mounted
1 projection screen
1 tripod base
3 barrel foot
•
Set up the experiment as in Fig. 1.
•
Insert the aluminium disc into the tube holder
from the rear.
•
Mount the pinhole aperture slide on the object
holder and position it close to the lamp.
•
Adjust the height of the components so that
the light beam passes through the cross lattice.
Fig. 1 Experiment set-up, 1 pinhole aperture slide, 2 lens, 3 aluminium disc
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Tel 0044 (0)1934 425333 • Fax 0044 (0)1934 425334 • e-mail uk3bs@3bscientific.com
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Technical amendments are possible
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3.2 Procedure
•
Perform the experiment using white light in a
darkened room
•
Vary the distance between the pinhole aper-
ture and the lens until the diffraction pattern is
visible on the screen.
•
First study the diffraction pattern when the
grid is not moving.
The diffraction pattern is similar to that of an elec-
tron beam diffracted through a polycrystalline
graphite lattice where all atoms are equally spaced.
•
Then rotate the disc rapidly.
The rotating grid simulates diffraction of an elec-
tron beam at a graphite lattice with a more or less
random distribution of atoms.
The way that the diffraction pattern depends on
the wavelength can easily be demonstrated with
the help of coloured filters. The diameter of the
diffraction rings gets smaller as the wavelength
decreases from red to green.
•
Hold the colour filters close to the pinhole
aperture.
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