Attach the deflection voltage circuit to either the
horizontal or the vertical deflection plate terminals. On which ever
pair you choose, be sure to remove the wire which connects the two
plates together, but not the wire which connects one of them to
ground. The other pair of plates should be left connected together
and grounded. Focus the beam at a high value of 
, say, greater
than 
V and see that the deflection voltage will
cause the spot to move.
Measure the deflection, D, as a function of deflection voltage,
, in both positive
and negative directions. Repeat the measurements for at least
two lower values of 
. Be sure to record the
values of 
and 
for each set of data.
Repeat the measurements for the other set of plates. Be sure to ground the pair of plates not in use.
Measure the length and separation of each pair of plates by sighting through the glass envelope of the tube. Use a plastic ruler or a short metric scale. Also measure the distance, L, of the pairs of plates from the screen.
Compute 
for each pair of data points 
,
using 
and plot a graph
of 
versus 
.
Be sure to plot both positive and negative values of
: locate the zero of your
coordinates at the center of the graph. On the same graph plot
vs. 
for the other values of 
. Label
the various lines on the graph for clarity and also label the axes
and include units.