___:
_
]
-
10—1.
INTRODUCTION
223
A streak of light may be seen back of a small hole in the
cathode of a discharge tube evacuated to approximately 0.01 mm. -
This is caused by the positively charged and neutral particles
‘
which have passed through the hole and are colliding.with mole—
cules of the residual gas.
The moving particles are called positive
-
(or canal) mys.* The charged particles or positive ions readily
lose their charge as they move through the gas so that they are '
usually studied in a very good vacuum (0.001 mm. of mercury or
less) by means of a willemite screen, photographie
mocouple or Faraday chamber.
_
The velocity of the positive rays can be measured by making
'
use of Doppler—’s principle. As the positive ions-move
from
the cathode, they undergo energy changes which result in the
emission of light. This light will show the usual spectrum of the
element making up the gas in the tube. Wave-length measure—
ments of one of these lines can be obtained from the side‘of the
'
beam and from directly in front,of it. Viewed end on, the wavelength from the moving particle is shifted t0Ward the blue end
_
of the spectrum as compared to that observed from the side.
,
Say the end—oh wave—length is
that from the side is À, then
the Doppler shift is >\ — >x’
,
and the velocity of the emitting source
IS
_
_
.
_
,
.
v =
'
:
‘
f
(10—1)
Where c is the velocity of…light, . The sh1ft1n'wave—length i_n“th€
.
Case of the blue
live
angstrom units. __The_
be
‘
around
Cclltimètcrs pçrsecond,ava1uewh1ch1ssmall_compared_
_Wi—th'that of the electronsmth<°»CÏISCÏWËCmbe "… '
7 i
.
'
:
-
;If‘ the
='VerYr I°"?
»
'
'
contmuedact10n0fafætpump1thllbeï‘f°‘Înd’
.
exponent1allawWithhÿdfogengasmthedISChargetube“S
iii“1ntenswspractlcallyzerof0ufœntlmeteleehlndthecathOde »
FromthisandthevelœyofthewnsthemaXlmumt1medumtwn —
5 mgraysthathavepassedthroughsmalloPemnâsTheyweredlsc°veredm
—
_
'
»
_
]
-
10—1.
INTRODUCTION
223
A streak of light may be seen back of a small hole in the
cathode of a discharge tube evacuated to approximately 0.01 mm. -
This is caused by the positively charged and neutral particles
‘
which have passed through the hole and are colliding.with mole—
cules of the residual gas.
The moving particles are called positive
-
(or canal) mys.* The charged particles or positive ions readily
lose their charge as they move through the gas so that they are '
usually studied in a very good vacuum (0.001 mm. of mercury or
less) by means of a willemite screen, photographie
mocouple or Faraday chamber.
_
The velocity of the positive rays can be measured by making
'
use of Doppler—’s principle. As the positive ions-move
from
the cathode, they undergo energy changes which result in the
emission of light. This light will show the usual spectrum of the
element making up the gas in the tube. Wave-length measure—
ments of one of these lines can be obtained from the side‘of the
'
beam and from directly in front,of it. Viewed end on, the wavelength from the moving particle is shifted t0Ward the blue end
_
of the spectrum as compared to that observed from the side.
,
Say the end—oh wave—length is
that from the side is À, then
the Doppler shift is >\ — >x’
,
and the velocity of the emitting source
IS
_
_
.
_
,
.
v =
'
:
‘
f
(10—1)
Where c is the velocity of…light, . The sh1ft1n'wave—length i_n“th€
.
Case of the blue
live
angstrom units. __The_
be
‘
around
Cclltimètcrs pçrsecond,ava1uewh1ch1ssmall_compared_
_Wi—th'that of the electronsmth<°»CÏISCÏWËCmbe "… '
7 i
.
'
:
-
;If‘ the
='VerYr I°"?
»
'
'
contmuedact10n0fafætpump1thllbeï‘f°‘Înd’
.
exponent1allawWithhÿdfogengasmthedISChargetube“S
iii“1ntenswspractlcallyzerof0ufœntlmeteleehlndthecathOde »
FromthisandthevelœyofthewnsthemaXlmumt1medumtwn —
5 mgraysthathavepassedthroughsmalloPemnâsTheyweredlsc°veredm
—
_
'
»