388
CONSTITUTION
OF
RADIATION
the secondary
cathode
rays depends
neither
on
the distance
between
the
plates
P1
and
P2
upon
which
they
impinge
nor on
the
intensity of
the
primary
cathode
rays,
but exclusively
on
the
velocity
of the
primary
cathode
rays.
Let
us
for
once assume
that this is
strictly
valid.
What
will
happen
if
we
let the
intensity
of the
primary
cathode
rays,
or
the size
of
the plate
P1
upon
which they
impinge,
decrease
to such
a
degree
that the
impinging
of
an
electron of the
primary
cathode
rays
can
be
conceived
as
an
isolated
process?
If the
above
is
really
true,
then, because the
velocity of
the
secondary
rays
is
independent
of the
intensity of
the
primary
rays,
we
will
have
to
assume
that
on
P2
(as
a
result
of
the
impinging
of
the
above
electron
on
P1)
either
nothing
is
being
produced
or
that
a
secondary
emission
of
an
electron
occurs on
it with
a
velocity of the
same
order
of
magnitude
as
of the electron
impinging
on
P1.
In
other
words,
the
elementary
radiation
process
seems
to
proceed
such
that it
does not,
as
the
wave
theory would
require,
distribute
and scatter
the
energy
of
the
primary
electron
in
a
spherical
wave
propagating
in
all directions.
Rather,
it
seems
that
at
least
a
large
part of this
energy
is available
at
some
location
of
P2
or
somewhere
else.
The
elementary
pro-
cess
of
radiation
seems
to
be
directed.
Furthermore,
one
gets
the
impression
that the
process
of
X-ray
production
in
P1
and
the
process
of
secondary
cathode
ray
production
in
P2
are
essentially
inverse
processes.
The
constitution of radiation thus
seems
to
be
different
from
that
following
from
our wave
theory. Important
clues
to
that effect
have been
provided
by
the
theory
of
temperature
radiation, first
and
foremost
by
the
theory
on
which
Mr.
Planck
has
based
his radiation formula. Since
I cannot
assume
that this
theory
is universally
known,
I will briefly describe its
[22]
essential points.
[21]
The
interior
of
a
cavity
of temperature
T
contains radiation
whose
composition
is
independent of
the
nature of
the
body.
The amount
of radiation
in the
cavity
,
whose frequency
lies
between
v
and
v +
dv,
is
pdv
per
unit
volume.
The problem
consists
of
determining
p as a
function of
v
and
T.
If
an
electric
resonator
of
proper
frequency
v0
and
slight attenuation
is
present
in the
cavity,
the
electromagnetic theory
of
radiation
enables
us
to
calculate the
time
average
of
the
energy (E)
of
the
resonator
as a
function
of
p(v0). The problem
is
thereby
reduced
to
one
of
determining
E
as a
function
of the
temperature. The
latter
problem
can
in
turn be
reduced
to
the