388
DOC. 24
DISCUSSION OF GDNA LECTURES
Doc.
24
Excerpts
of
Discussions
Following
Lectures
Delivered
at 83rd
Meeting
of
the Gesellschaft Deutscher Naturforscher und
Arzte,
25
and
27
September
1911
[Physikalische
Zeitschrift
12
(1911): 978, 1068-1069,
and
1084]
Stark:
The
speaker
said
that
an
electron
resonates
without
damping
in
response
to
incident monochromatic radiation until the time
a
quantum
of
action, or,
to
use
the
Planck-Einstein
expression,
an
energy quantum
has
accumulated
in it. I would like to ask
whether
a
calculation has
been
performed regarding
the
length
of time the
resonance
needs for the
accumulation
of
a
light
quantum.
This
question comes
to mind because it
was precisely
Lorentz
who
performed
detailed
calculations
on
this
point
and
who
pointed
out
that, even
in
the
case
of
perfect undamped resonance,
the
lengths
of
time
one
would
have to
assume
in
order
to
explain
the
maximum
kinetic
energy
in
the
photoelectric
effect
are so
great
that
they
cannot
be reconciled
to within
an
order of
magnitude
with
the
actually
observed situation
regarding
the
intensity
and maximum
kinetic
energy
of the
emitted
ions.
Sommerfeld:
Of
course,
the
magnitudes
that Lorentz found
for
the
time
length
t
are
here
valid
for
monochromatic
light
within
the
same
order of
magnitude.
It
can
be
shown
that
our
results
are
not
confined
to
monochromatic
light,
and this must
be
shown
because monochromatic
light
does not exist.
If
one uses
natural
light as
the incident
light,
and the
laws
found for monochromatic
light
remain
valid
up
to
the
dispersion
mentioned,
then the
difficulty
regarding
the
time
length is
eliminated.
Stark:
But the
light
that
was
used
in
spectral
resolution
was
practically
monochromat-
ic. Ladenburg
worked
with
the
lines
of the
mercury
arc.
Their
frequency range is
very
narrow.
Have
you
performed
the
calculation
for
a
specific
frequency range?
For
example,
for
a
spectral
line with
a
width
of
1
ängstrom.
Sommerfeld: Yes,
for
one
spectral
line.
Stark:
The
consistency
of
such
a
result
with
Lorentz's
calculation would
be
amazing
indeed.
I
assume
that
a
detailed
report
of the
calculation
is
to follow?
Einstein:
Would the time
required
for
a
complete
act
of
absorption
according
to
the
[1]
theory presented
not be
long
enough
to
be
accessible to
observation? In
this
case,
the
experimental
investigation
would
be of
enormous
interest.
Sommerfeld:
I believe
that
it would be
possible
to
compare
the theoretical
[2]
accumulation time
with
experiment.
Stark:
Can the
resonance theory presented
be
extended
to the emission
of cathode
rays
to
the
Roentgen-induced rays?
This would
be desirable because the
phenomenon
in
question
is
completely
analogous
to
the
photoelectric
effect.