J
5—6.
VARIOUS FILAMENTS
109
il
in amperes per s'quare centimeterof surface of the lament. On
the other hand, it is not necessary to know the area of the lament
in
order to prove that
Richardson’s equation is
Y_
.
of the correct form; or to
'
determine the value of the -
c
work function çb. The neg—
ative slope of the straight
'
line in gure 5—6 is equal
_
,
to
Ay/Ax and involves &“
Ay {
_
the difference Ay between
L—A—X"
two values of loglo(is/T2).
59
_
Then the area of the la—
,
'
ment dropsout and ob'
served
currents
for
the
X
particular lament under
_
+
_
'test may be used.
When
FIG. 5—6.
Testing Richardson’s equation.
‘ is in ergs per electron
..
( 5.491» of chapter ,
the slope m is equal to 0.4343w/Æ. Changing
to volts per e;sä»u., by the use of equation 4—,14, we nd
.
’
CValues of çb;for_ varÏicS;matéälswäll berf0uhd in Table 1.
.
The smaller the…
m0regcopious the emission Of
electrons,
“being
the. Work
—
_
£unctio;.i3
large:
:_
Willä ble
the
'
-
precedlngchapterontheph@toelectrlceffect
.
*
—
-—…
.
wherebetween2@Kand220Kïnfact1œtheælûmæd ‘ Ï