96
4.
PHOTOELECTRIC EMISSION
‘
—
V
"
‘
.
"
'
=
L'
P
L2
'
s
2
-
'
-
!
(â )
[IJ
=â
vs
(b)
Ke
(°)
R. F—
-
_I’_W_
R
R
,
W/W.ËW
”
.…
_
%
=
_
:
—
+
noue. —.
FIG. 4—16.
Apparatus for the measurement of iz/e.
tate the starting of the arc. The choke L may be used, although
it is not essential, in order to steady the light by reducing uc—
tuatios inthe line voltage. If an alternating current arc is used
its enclosing shield must be grounded.
The prism P is a large glass or C82 type With faces four centi—
meters or more on the side. Liquid solder has been found satisfactory in sealing the glasssides to the framework of a C82 prism.
'
The lenses L1 and L2 are cheap reading glasses of 20 to 40
c€ntimeters focal length. L1 has its focus at approximately 8152
and L2 is arranged
to give a streak of light on the edge of
“
sens1tive surface of the photo—cell C. The Width of this streak
is kept constant at approximately 2 millimeters._ The reason for
nOt 111uminating the entire cathode may be explained as follows:
1f the cathode is not concentric With the anode, differing compo—
nents of the motion of the electrons from various parts of the
7
1
be eëctive, and retarding potential values will'n0t‘
bÇ, sharp- ‘It—‘is tobe noted in the gure that the light does hot
—
anode and produce photo—elections at this point. The”
ShtïOpenings’:=ardaas{fOHOWS:' 82, 1«;millimeter by 2.5
2.5 centimeters, 84—, 3 millimeters by 25
»centifneters. Slit 84 should
becurved
lines are‘
;The apparatus shoul1
4.
PHOTOELECTRIC EMISSION
‘
—
V
"
‘
.
"
'
=
L'
P
L2
'
s
2
-
'
-
!
(â )
[IJ
=â
vs
(b)
Ke
(°)
R. F—
-
_I’_W_
R
R
,
W/W.ËW
”
.…
_
%
=
_
:
—
+
noue. —.
FIG. 4—16.
Apparatus for the measurement of iz/e.
tate the starting of the arc. The choke L may be used, although
it is not essential, in order to steady the light by reducing uc—
tuatios inthe line voltage. If an alternating current arc is used
its enclosing shield must be grounded.
The prism P is a large glass or C82 type With faces four centi—
meters or more on the side. Liquid solder has been found satisfactory in sealing the glasssides to the framework of a C82 prism.
'
The lenses L1 and L2 are cheap reading glasses of 20 to 40
c€ntimeters focal length. L1 has its focus at approximately 8152
and L2 is arranged
to give a streak of light on the edge of
“
sens1tive surface of the photo—cell C. The Width of this streak
is kept constant at approximately 2 millimeters._ The reason for
nOt 111uminating the entire cathode may be explained as follows:
1f the cathode is not concentric With the anode, differing compo—
nents of the motion of the electrons from various parts of the
7
1
be eëctive, and retarding potential values will'n0t‘
bÇ, sharp- ‘It—‘is tobe noted in the gure that the light does hot
—
anode and produce photo—elections at this point. The”
ShtïOpenings’:=ardaas{fOHOWS:' 82, 1«;millimeter by 2.5
2.5 centimeters, 84—, 3 millimeters by 25
»centifneters. Slit 84 should
becurved
lines are‘
;The apparatus shoul1