72
4.
PHOTOELECTRIC EMISSION
.
and the ordiriates of the relative energy curve of the source (figure
4—6) give the currents Which are observed.
'
If, instead of a monochromatic beam of light, the total radiation
from a source is allowed to fall upon
a photoelectric surface, the
current Will be the integrated effect of all the separate wave.
lengths to which the surface responds, i.e., the area under the
“
observed
”
current curve mentioned in the preceding paragraph.
_
If a metal cathode is exposed to the total radiation of a black body
*
.
operated
at a temperature
of T degrees absolute, the total or
complete photoelectric
current ic from the surface is given by
hyo
_
.
i,,— = ÆT2é_
(4—3)
where 6 is the base of the Naperian logarithm system, 41, &, and k
are constants and v,, is the threshold frequency corresponding to
,
the long-wave-length limit )….
‘îî
'
If plane polarized light of a given wave-length and intensity
r…Î
falls obliquely on a given surface, the number of electrons ejected
-
may
be varied by rotating the plane of polarization. Whenever
the electric vector of the light has a larger component which
“
cuts
”
into the surface, there is'an increase in the number of
electrons given off perpendicularly to that surface. Now, it has
been noted that the am0unt of light absorbed by a surface changes
,
as the plane of polarization of the incident light is rotated. Con—
sider the photoelectric currents produced when the plane of polarization is at two different angles. If the ratio of the currents is not
'
the same as the ratio of the amounts of light absorbed by the
surface in the two cases, polarization selectivity is said to occur. '
*
Polarization and spectral selectivity very frequently occur together. ,
TO specify the output of a photoelectric cell, it is necessary
to
include the intensity, the wave-length, the state of polarization
Î’j —
and the”’angle of incidence of the light.
.
«
,
_
4—3 Measurement
of the Sensitivity orYield,—The spectral“
f
photoelectric yield is dened as the quantity of
second by unit intensity of absorbed
'_
* For
“
black” body, its calor temperatùr€ may be used.
-_:Ï
E‘Ëâbsolüte,*isy the
to Whichan
black body Would
“°edmbeheated
the, actual temperature
°ftheb0dy_,
sky;
may have a color tem
.:
K ‘
>
'
;
"
1
f
‘
'
x
4.
PHOTOELECTRIC EMISSION
.
and the ordiriates of the relative energy curve of the source (figure
4—6) give the currents Which are observed.
'
If, instead of a monochromatic beam of light, the total radiation
from a source is allowed to fall upon
a photoelectric surface, the
current Will be the integrated effect of all the separate wave.
lengths to which the surface responds, i.e., the area under the
“
observed
”
current curve mentioned in the preceding paragraph.
_
If a metal cathode is exposed to the total radiation of a black body
*
.
operated
at a temperature
of T degrees absolute, the total or
complete photoelectric
current ic from the surface is given by
hyo
_
.
i,,— = ÆT2é_
(4—3)
where 6 is the base of the Naperian logarithm system, 41, &, and k
are constants and v,, is the threshold frequency corresponding to
,
the long-wave-length limit )….
‘îî
'
If plane polarized light of a given wave-length and intensity
r…Î
falls obliquely on a given surface, the number of electrons ejected
-
may
be varied by rotating the plane of polarization. Whenever
the electric vector of the light has a larger component which
“
cuts
”
into the surface, there is'an increase in the number of
electrons given off perpendicularly to that surface. Now, it has
been noted that the am0unt of light absorbed by a surface changes
,
as the plane of polarization of the incident light is rotated. Con—
sider the photoelectric currents produced when the plane of polarization is at two different angles. If the ratio of the currents is not
'
the same as the ratio of the amounts of light absorbed by the
surface in the two cases, polarization selectivity is said to occur. '
*
Polarization and spectral selectivity very frequently occur together. ,
TO specify the output of a photoelectric cell, it is necessary
to
include the intensity, the wave-length, the state of polarization
Î’j —
and the”’angle of incidence of the light.
.
«
,
_
4—3 Measurement
of the Sensitivity orYield,—The spectral“
f
photoelectric yield is dened as the quantity of
second by unit intensity of absorbed
'_
* For
“
black” body, its calor temperatùr€ may be used.
-_:Ï
E‘Ëâbsolüte,*isy the
to Whichan
black body Would
“°edmbeheated
the, actual temperature
°ftheb0dy_,
sky;
may have a color tem
.:
K ‘
>
'
;
"
1
f
‘
'
x