sliwa richard franck hertz

8/3/2019 Sliwa Richard Franck Hertz

1/19

Frank Hertz ExperimentFrank Hertz Experiment

Ben Richard and Katrina SliwaBen Richard and Katrina Sliwa

PHY243WPHY243W


2/19

Preview of Things to ComePreview of Things to Come

HistoryHistory

TheoryTheory

ApparatusApparatus

IonizationIonization

ExcitationExcitation

ShieldingShielding ConclusionsConclusions


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HistoryHistory

In 1914, by James Franck and Gustav Ludwig HertzIn 1914, by James Franck and Gustav Ludwig Hertz

One year after Bohrs theory of quantized energy statesOne year after Bohrs theory of quantized energy states

Nobel Prize in 1925: for their discovery of the lawsNobel Prize in 1925: for their discovery of the laws

governing the impact of an electron upon an atomgoverning the impact of an electron upon an atom

Photos: Copyright The Nobel Foundation


4/19

Energy LevelsEnergy Levels

Bohr: discrete energy levelsBohr: discrete energy levels

Excite electrons with electron impactExcite electrons with electron impact

Hg: 80 electronsHg: 80 electrons

Excited transitions from electronsExcited transitions from electrons

33PP00

11SS00 ((4.6 eV)4.6 eV)

33PP11 11SS00 ((4.9 eV)4.9 eV)

33PP22

11SS00 ((5.4 eV)5.4 eV)

11PP11

11SS00 ((6.7 eV)6.7 eV)


5/19

Electron ScatteringElectron Scattering

Why Hg?Why Hg?

Monoatomic vaporMonoatomic vapor

Easy to control vapor pressureEasy to control vapor pressure

Mean free path through a gas in a cavity:Mean free path through a gas in a cavity:

I = (2I = (2nRnR00))--

Kinetic energy gained in an electric field during I:Kinetic energy gained in an electric field during I:

K = eEIK = eEI

Elastic scattering: K


6/19

Frank Hertz Vacuum TubeFrank Hertz Vacuum Tube

Anode

Cathode (VF)

Grid (VCG

)

Electric field


7/19

Frank HertzBox

Control Box

MultimeterElectrometer

To Computer

A

G

F C

Experimental SetupExperimental Setup

Thermometer

B


8/19

IonizationIonization

Anode at negative potential w.r.t. cathodeAnode at negative potential w.r.t. cathode

Grid at positive potential w.r.t. cathodeGrid at positive potential w.r.t. cathode

Electrons can ionize mercuryElectrons can ionize mercury

positive Hg ions pulled toward anodepositive Hg ions pulled toward anode

SettingsSettings

Retarding voltage: 1.5 VRetarding voltage: 1.5 V VVff= 6.3 V= 6.3 V

Temperature from 100Temperature from 10000C to 185C to 18500CC


9/19

Temperature ResultsTemperature Results


10/19

Ionization ResultsIonization Results


11/19


12/19

ExcitationExcitation

Retarding voltage: 1.5 VRetarding voltage: 1.5 V VVff= 6.30 V= 6.30 V

0 V < V0 V < Vcgcg < 45 V in 0.1 V steps< 45 V in 0.1 V steps

Assumptions:Assumptions:

KKe cathodee cathode= 0= 0

All electrons with KAll electrons with K

ee < eV< eV

retardingretarding captured by gridcaptured by grid

Electrons with required energy travel negligibleElectrons with required energy travel negligible

distances before collisiondistances before collision


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Excitation resultsExcitation results


14/19

Excitation resultsExcitation results

Avg dist between peaks: 4.93Avg dist between peaks: 4.93+/- .25 eV+/- .25 eV For Hg:For Hg:E = 4.6 eV, 4.9 eV, 5.4 eV, 6.7 eVE = 4.6 eV, 4.9 eV, 5.4 eV, 6.7 eV

LifetimeLifetime

33

PP00 11

SS00 >> Lifetime>> Lifetime33

PP11 11

SS00 Accepted value: 4.9 eVAccepted value: 4.9 eV

h = Veh = Ve/c;/c; = 253.6 x 10= 253.6 x 10-9-9 mm

h = 6.63 +/- .34 x 10h = 6.63 +/- .34 x 10-34-34 JsJs

Accepted value: h=Accepted value: h=6.626 x 106.626 x 10-34-34 JsJs


15/19

Excitation ObservationsExcitation Observations


16/19

Excitation ObservationsExcitation Observations

www.physics.umd.edu/.../demos/demosn2/n2-06.htm
http://www.physics.umd.edu/.../demos/demosn2/n2-06.htmhttp://www.physics.umd.edu/.../demos/demosn2/n2-06.htmhttp://www.physics.umd.edu/.../demos/demosn2/n2-06.htmhttp://www.physics.umd.edu/.../demos/demosn2/n2-06.htm


17/19

ElectrometerElectrometer

Very sensitive to external electric fieldsVery sensitive to external electric fields

Attempted to create grounded tin foil shieldAttempted to create grounded tin foil shield


18/19

ConclusionsConclusions

Inconclusive ionization resultsInconclusive ionization results

Found excitation peaks at: 4.93Found excitation peaks at: 4.93 +/- .25 eV+/- .25 eV

Measured h to be: 6.63 +/- .34 x 10Measured h to be: 6.63 +/- .34 x 10-34-34

JsJs Future work:Future work:

Fine tune parameters for ionizationFine tune parameters for ionization

Obtain VObtain Vff experimentallyexperimentally Create better shield for electrometerCreate better shield for electrometer


19/19

ReferencesReferences

UR Advanced Laboratory Manual, The Franck-HertzExperiment [Online]http://www.pas.rochester.edu/~AdvLab/2-Frank-Hertz/La

K. M. Beck and J. Mainzer, The Franck-HertzExperiment [Online] http://www.pas.rochester.edu/~advlab/reports/beck_mainzer_franckhertz.pdf

A. C. Melissinos, Experiments in Modern PhysicsAcademic Press (1966)

C. J. SansonettiC. J. Sansonetti et al.et al., Phys. Scr., Phys. Scr. 6363 219-242, 2001219-242, 2001

Nobel FoundationNobel Foundationhttp://nobelprize.org/nobel_prizes/physics/laureahttp://nobelprize.org/nobel_prizes/physics/laureates/1925/index.htmltes/1925/index.html
http://www.pas.rochester.edu/~AdvLab/2-Frank-Hertz/Lab02%20Hertz.pdfhttp://www.pas.rochester.edu/~advlab/reports/http://www.pas.rochester.edu/~advlab/reports/http://www.pas.rochester.edu/~advlab/reports/http://www.pas.rochester.edu/~advlab/reports/http://www.pas.rochester.edu/~advlab/reports/http://www.pas.rochester.edu/~advlab/reports/http://www.pas.rochester.edu/~advlab/reports/http://www.pas.rochester.edu/~advlab/reports/http://www.pas.rochester.edu/~advlab/reports/http://www.pas.rochester.edu/~AdvLab/2-Frank-Hertz/Lab02%20Hertz.pdf

sliwa richard franck hertz

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