_
4—4.
PRACTÎCAÏ. UNITÉ
*
73
light of a given freqbency. The measurement of the quantity of
electricity emitted-each second, i.e., the photoelectric current,
is easily accomplished; but an absolute determination of the
intensity of the light absorbed is morediicult. This “
intensity,”
in basic form, is expressed as the number of ergs absorbed by unit
area each second.
Since 4.18 >< 107 ergs are the equivalent of
one calorie, the intensity measurement may be made in terms of
the heat produced in a given body “each second
same
monochromatic beam of light which is used to'liberate the electrons.
Thus one may use a thermocouple whose currents have previously
been calibrated in terms of the number of calories of heat absorbed
each second.
The yield is then obtained in coulombs—per—second
per calorie—per-second or, as usually expressed, in coulombs per
calarie.
The yield is also commonly expressed in amperes par wdz‘z‘. ‘
For example, the measured yield of a potassium surface, sensitized
With hydrogen and irradiated with blue light of wave—length 4500
_
angstroms, was found to be 0.015 coulombs per calorie. This is
equal to 000358 coulombs-per-second per joule—per—second or
.
000358 amperes per watt. The yield in commercial cells ranges
from zero to ten micr0amperes Of photoelectric current per micro,
watt of radiant energy.
'
For comparative work, where the general shape but not the
absolute values of the curves iÏ1‘ gure 4—5
desiréd, the relative
_
response
at the different
is speCiedas_ the ratio of
.
the phOtoélectriC Current *to‘ “the"?
current 2'produced' by a black
su'rfaced
with“? thesaihe light; This assumes
_
that the thermop‘ev currenœare d1rectlyproportional to ”the“ heat
-
in Ord‘e‘f=that the “
_“
absorptionofenergywlbe,asnearlyagp0331ble,complete at {the
calledthelumenlsthatamwntofhghtmdmthmaumtS°hd T‘,
H…… "i“'l‘liîi‘Willi “‘illinl‘rl'iîliïlliliîil‘flîî‘“ ………………
4—4.
PRACTÎCAÏ. UNITÉ
*
73
light of a given freqbency. The measurement of the quantity of
electricity emitted-each second, i.e., the photoelectric current,
is easily accomplished; but an absolute determination of the
intensity of the light absorbed is morediicult. This “
intensity,”
in basic form, is expressed as the number of ergs absorbed by unit
area each second.
Since 4.18 >< 107 ergs are the equivalent of
one calorie, the intensity measurement may be made in terms of
the heat produced in a given body “each second
same
monochromatic beam of light which is used to'liberate the electrons.
Thus one may use a thermocouple whose currents have previously
been calibrated in terms of the number of calories of heat absorbed
each second.
The yield is then obtained in coulombs—per—second
per calorie—per-second or, as usually expressed, in coulombs per
calarie.
The yield is also commonly expressed in amperes par wdz‘z‘. ‘
For example, the measured yield of a potassium surface, sensitized
With hydrogen and irradiated with blue light of wave—length 4500
_
angstroms, was found to be 0.015 coulombs per calorie. This is
equal to 000358 coulombs-per-second per joule—per—second or
.
000358 amperes per watt. The yield in commercial cells ranges
from zero to ten micr0amperes Of photoelectric current per micro,
watt of radiant energy.
'
For comparative work, where the general shape but not the
absolute values of the curves iÏ1‘ gure 4—5
desiréd, the relative
_
response
at the different
is speCiedas_ the ratio of
.
the phOtoélectriC Current *to‘ “the"?
current 2'produced' by a black
su'rfaced
with“? thesaihe light; This assumes
_
that the thermop‘ev currenœare d1rectlyproportional to ”the“ heat
-
in Ord‘e‘f=that the “
_“
absorptionofenergywlbe,asnearlyagp0331ble,complete at {the
calledthelumenlsthatamwntofhghtmdmthmaumtS°hd T‘,
H…… "i“'l‘liîi‘Willi “‘illinl‘rl'iîliïlliliîil‘flîî‘“ ………………