PASCO SE-9639 User Manual
Instruction Manual
Franck-Hertz Experiment
012-14264A
Model SE-9639
Brolight Technology Co., Ltd
®
Table of Contents
Equipment List - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1
Limited Warranty and Limitation of Liability - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2
Safety Information - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2
Installation and Maintenance- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3
Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5
Principle of the Experiment - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5
Experiment Procedure 1 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 11
Experiment Procedure 2 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 14
Appendix A: General Specifications - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 18
Appendix B: Teacher’s Notes - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 19
Appendix C: Technical Support, Copyright, Warranty - - - - - - - - - - - - - - - - - - - - - - - - 23
Product End of Life Disposal Instructions - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 23
ii
Instruction Manual
1
2
3
4
5, 6, 7, 8
Adjust:
0 – 6.3 V
Adjust:
-4.5 V – 0 V
and
-4.5 V – +30 V
Select:
-4.5 V – 0 V
-4.5 V – +30 V
Select:
0 – 100 V
0 – 200 V
Adjust:
0 – 100 V
and
0 – 200 V
Adjust:
0 – 12 V
Select:
MEASURE
CALIBRATION
Adjust:
CURRENT
Select:
CURRENT
RANGES
9
Franck-Hertz Experiment
012-14264A
SE-9639
Equipment List
Included Equipment Model Quantity
1. Tunable DC (Constant Voltage) Power Supply I SE-6615 1
2. Tunable DC (Constant Voltage) Power Supply II SE-9644 1
3. DC Current Amplifier SE-6621 1
4. Argon Tube Enclosure with Argon Tube SE-9650 1
5. Connecting cable, 850 mm, red EM-9740 Set of 5
6. Connecting cable, 850 mm, black EM-9745 Set of 5
7. Power Cord - 3
8. BNC Cable - 1
9. 8-pin DIN Extension Cable UI-5218 2
012-14264A
1
SE-9639 Franck-Hertz Experiment
WARNING: To avoid possible electric shock or personal history, follow these guidelines.
Recommended Items
Item Model Quantity
850 Universal Interface UI-5000 1
PASCO Capstone Software UI-5400 1
Limited Warranty and Limitation of Liability
This Brolight product is free from defects in material and workmanship for one year from the date of purchase. This warranty
does not cover fuses, or damage from accident, neglect, misuse, alteration, contamination, or abnormal conditions of operation
or handling. Resellers are not authorized to extend any other warranty on Brolight’s behalf. To obtain service during the warranty period, return the unit to point of purchase with a description of the problem.THIS WARRANTY IS YOUR ONLY
REMEDY. NO OTHER WARRANTIES, SUCH AS FITNESS FOR A PARTICULAR PURPOSE, ARE EXPRESSED OR
IMPLIED. BROLIGHT IS NOT LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSSES, ARISING FROM ANY CAUSE OR THEORY. Since some states or countries do not allow the exclusion
or limitation of an implied warranty or of incidental or consequential damages, this limitation of liability may not apply to you.
Safety Information
• Do not clean the equipment with a wet cloth.
• Before use, verify that the apparatus is not damaged.
• Do not defeat power cord safety ground feature.
• Plug into a grounded (earthed) outlet.
• Do not use the product in any manner that is not specified by the manufacturer.
• Do not install substitute parts or perform any unauthorized modification to the product.
• Line and Current Protection Fuses: For continued protection against fire, replace the line fuse and the
current-protection fuse only with fuses of the specified type and rating.
• Main Power and Test Input Disconnect: Unplug instrument from wall outlet, remove power cord, and
remove all probes from all terminals before servicing. Only qualified, service-trained personnel should
remove the cover from the instrument.
• Do not use the equipment if it is damaged. Before you use the equipment, inspect the case. Pay particular
attention to the insulation surrounding the connectors.
• Do not use the equipment if it operates abnormally. Protection may be impaired.
• When in doubt, have the equipment serviced.
• Do not operate the equipment where explosive gas, vapor, or dust is present. Don't use it under wet
conditions.
• Do not apply more than the rated voltage, as marked on the apparatus, between terminals or between any
terminal and earth ground.
• When servicing the equipment, use only specified replacement parts.
• Use caution when working with voltages above 30 V AC rms, 42 V peak, or 60 V DC. Such voltages pose
a shock hazard.
• To avoid electric shock, do not touch any bare conductor with hand or skin.
• Adhere to local and national safety codes. Individual protective equipment must be used to prevent shock
and arc blast injury where hazardous live conductors are exposed.
2
012-14264A
Franck-Hertz Experiment Electrical Symbols
WARNING:
To reduce the risk of electric shock or damage to the instrument, turn the power switch off and
disconnect the power cord before replacing a tube.
• Special note: If a dangerous voltage is applied to an input terminal, then the same voltage may occur at all
other terminals.
Electrical Symbols
Alternating Current
Direct Current
Caution, risk of danger, refer to the operating manual
before use.
Caution, possibility of electric shock
Earth (ground) Terminal
Protective Conductor Terminal
Chassis Ground
Conforms to European Union directives.
WEEE, waste electric and electronic equipment
Fuse
On (Power)
Off (Power)
In position of a bi-stable push control
Out position of a bi-stable push control
Installation and Maintenance
012-14264A
3
SE-9639 Franck-Hertz Experiment
• Note: The tube is a thin-walled, evacuated glass bulb. Handle with
care! Do not expose the tube to mechanical stress or strain.
Note: Replace the argon tube with the same type: Model SE-9645 Franck-Hertz Ar-Tube.
The fuse is inside a
tray. Open the
cover to remove
the fuse.
WARNING
To reduce the risk of electric shock or
damage to the instrument, turn the
power switch OFF and disconnect the
power cord before replacing a fuse.
Fuse Cover Tray
Pry
here
Note: Replace the burned fuses with new fuses of the same type. (One spare fuse is included.)
Replace the Argon Tube
• Use a flat-blade screwdriver to remove the two small screws that hold the back
plate onto the argon tube enclosure.
• Use a small flat-blade screwdriver to pry the back panel off of the enclosure.
• Pull up on the elastic pressing spring and rotate it off the argon tube.
• Gently pull out the argon tube.
• Then, install a new tube and replace the elastic pressing spring.
• Finally, close the case and replace the two small screws.
Argon Tube Specifications
Filling gas argon
Filament voltage 6.3 V DC
Accelerating voltage 100 V DC
Wave crest (or trough) number 6
Life span 2000 hours
Fuse Replacement
• Disconnect the power cord from the instrument.
• Open the fuse cover and remove the fuse. (The fuse is inside a tray. Use a small
screwdriver or other tool to pry the tray open.)
• Replace the fuse(s). Use the same type of fuse (250 V T2A).
• Reconnect the power cord and turn on the instrument.
• If the problem persists, contact Brolight Corporation for service.
4
012-14264A
Franck-Hertz Experiment Introduction
Introduction
In 1914, James Franck and Gustav Hertz discovered in the course of their investigations an “energy loss in distinct steps
for electrons passing through mercury vapor”, and a corresponding emission at the ultraviolet line (= 254 nm) of mer-
cury. As it is not possible to observe the light emission directly, demonstrating this phenomenon requires extensive and
cumbersome experiment apparatus. They performed this experiment that has become one of the classic demonstrations
of the quantization of atomic energy levels. They were awarded the Nobel Prize for this work in 1925.
In this experiment, we will repeat Franck and Hertz's energy-loss observations, using argon, and try to interpret the data
in the context of modern atomic physics. We will not attempt the spectroscopic measurements, since the emissions are
weak and in the extreme ultraviolet portion of the spectrum.
Principle of the Experiment
The Franck-Hertz tube is an evacuated glass cylinder with four electrodes (a “tetrode”) which
contains argon. The four electrodes are: an indirectly heated oxide-coated cathode as an electron
source, two grids G
1 (G
) is positive with respect to the cathode (K) (about 1.5 V). A variable potential difference is
1
applied between the cathode and Grid 2 (G
accelerated to a range of electron energies. The distance between the cathode and the anode is
large compared with the mean free path length in the argon in order to ensure a high collision
probability. On the other hand, the separation between G
small. A small constant negative potential U
and the collector plate A (i.e. A is less positive than G
and collector electrode A opposes the motion of electrons to the collector electrode, so that electrons which have kinetic energy less than e•U
As will be shown later, this retarding voltage helps to differentiate the electrons having inelastic
collisions from those that don’t.
and G2 and a plate A which serves as an electron collector (anode A). Grid
1
) so that electrons emitted from the cathode can be
2
and the collector electrode (A) is
(“retarding potential”) is applied between G2
G2A
G2A
2
). The resulting electric field between G2
2
at Grid 2 cannot reach the collector plate A.
A sensitive current amplifier is connected to the collector electrode so that the current due to the
electrons reaching the collector plate may be measured. As the accelerating voltage is increased,
the following is expected to happen: Up to a certain voltage, say V
increase as more electrons reach the plate. When the voltage V is reached, it is noted that the plate current, I
sudden drop. This is due to the fact that the electrons just in front of the grid G
, the plate current IA will
1
have gained enough energy to collide
2
, takes a
A
inelastically with the argon atoms. Having lost energy to the argon atom, they do not have sufficient energy to overcome the retarding voltage between G
and collector electrode A. This causes a decrease in the plate current IA. Now as
2
the voltage is again increased, the electrons obtain the energy necessary for inelastic collisions before they reach the
anode. After the collision, by the time they reach the grid, they have obtained enough energy to overcome the retarding
voltage and will reach the collector plate. Thus I
that I
drops. This means that the electrons have obtained enough energy to have two inelastic collisions before reach-
A
ing the grid G
again, I
, but have not had enough remaining energy to overcome the retarding voltage. Increasing the voltage
2
starts upward until a third value, V3, of the voltage is reached when IA drops. This corresponds to the elec-
A
trons having three inelastic collisions before reaching the anode, and so on. The interesting fact is that V
V
- V1, etc., which shows that the argon atom has definite excitation levels and will absorb energy only in quantized
2
will increase. Again when a certain voltage V2 is reached we note
A
- V2 equals
3
amounts.
012-14264A
5
SE-9639 Franck-Hertz Experiment
Figure 1.1: Franck-Hertz tube
Figure 1.2: Anode current curve
he
U
0
c
------
=
When an electron has an inelastic collision with an argon atom, the kinetic
energy lost to the atom causes one of the outer orbital electrons to be
pushed up to the next higher energy level. This excited electron will within
a very short time fall back into the ground state level, emitting energy in
the form of photons. The original bombarding electron is again accelerated
toward the grid anode. Therefore, the excitation energy can be measured in
two ways: by the method outlined above, or by spectral analysis of the
radiation emitted by the excited atom.
Figure 2 displays a typical measurement of the anode current, I
a function of the accelerating voltage. As soon as V
current increases with rising V
decreases for a voltage U
and then increases up to U2, and then
1
. Notice that the current sharply
G2K
G2K
> V
G2A
A
the
, as
this pattern recurs. The interpretation of these observations is successful with the following assumptions:
• Having reached energy of about e•U
, electrons can transmit
0
their kinetic energy to a discrete excitement state of the argon
atoms.
• As a result of the inelastic collision, they pass the braking volt-
age.
• If their energy is twice the required value, or 2 e•U
, they can
0
collide two times inelastically and similarly for higher voltages.
• As a matter of fact, a strong line can be found for emission and absorption corresponding to an energy of e•U
tation energy of argon, in the optical spectrum (108.1 nm).
In figure 2, the resonance voltage is denoted by U
e•U
= hƒ = hc/
0
.
0
or
, the exci-
0
where e is the charge on an electron, h is Planck’s Constant, and c is the speed of light.
6
012-14264A
Loading...