3B SCIENTIFIC PHYSICS U19153 Manuel D'utilisation page 7

mounted on stand equipment (refer to Fig. 4).
•
Set up the experiment as in Fig. 3. Connect the
minus-pole of the anode voltage to the 4-mm
socket marked with a minus.
•
Turn on the power supply for the tube and
observe the shadow.
•
Turn on the coil current and slowly increase it.
By increasing the magnetic field (raising the voltage
to the coil) the image is seen to rotate, diminish to
a spot and then enlarge again in inverted form.
Anode voltage variations provide a further element
of control.
Cathode rays and deflecting fields can thus be used
to magnify shadow images in a manner analogous
to an optical lens system.
Fig. 1 Linear propagation of cathode rays
Fig. 2 Electrostatic charging effects
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