THE ATOM
PHYSICS IS PHUN - January 2008
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Please take a grating
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Please be Seated
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Program tonight is THE ATOM
Tonight we will discuss concepts in sub-microscopic physics.
To do this we must use indirect experiments and models.
Make sure you have a grating
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The Elements, by Tom Lehrer
ELECTROMAGNETIC SPECTRUM
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K8-01 ELECTROMAGNETIC WAVE - MODEL
Comment: Variety of EM waves - all obey the equation
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c=f
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EM Spectrum by frequency, wavelength, and photon energy (neglect now)
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N1-05 SPECTRA - VISIBLE AND INVISIBLE
Comment: UV using fluorescein dye, IR using thermocouple
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Duality of Light
Comment: photon behavior of light/EM waves - great paradox of physics
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E=hf (NOTE: Einstein Nobel Prize for this)
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Boiling Water and the Photoelectric Effect
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P2-02 PHOTOELECTRIC EFFECT IN ZINC - ARC LAMP
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EM Spectrum by frequency, wavelength, and photon energy
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P2-05 PHOTO-RESISTOR RELAY
Comment: operates street lamps using photoelectric effect
Examples: photoelectric calculators, experimental car (UM)
(page 2)
ATOMIC STRUCTURE AND TRANSITIONS
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Atomic Structure
Review:
Atom = nucleus with electrons in orbit around nucleus
simple model - like planets revolving around sun
typical size ~ 10-10 meters
Nucleus = protons and neutrons
typical size ~ 10-15 meters
most mass in nucleus; electrons ~ 1 part in 4000
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P3-53 ATOMIC ENERGY LEVEL MODEL
Comment: Higher level is less strongly bound, larger electron radius
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Periodic Table
Comment: Energy level structure leads to periodic table and line spectra
Alternatively: these are evidence of atomic energy levels
Stable inert gases: He, Ne, Ar
Extra electron share it: H, Li
Lacking electron grab it: Fl, Cl
Comment on Periodic Table of the Elements
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Atomic Spectra – list ones to be seen here
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Black
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Diffraction spectrum of white light with gratings
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P3-51 BALMER SERIES with TV
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Hydrogen atomic transitions
Comments:
n=1 series UV (Lyman)
N=2 series (Balmer) visible
N=3 series IR (Paschen)
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Black
(page 3)
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N2-02 DIFFRACTION SPECTRA - THREE SOURCES - EXPENDABLE GRATINGS
White light, Mercury, Cadmium
Comments: Heat creates continuous spectrum
Atomic electron transitions create line spectra
Discrete energy levels create discrete spectra
All atoms and/or molecules have different spectra (structure)
Comment: ID materials, drugs, etc.
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N2-03 DIFFRACTION SPECTRUM OF SODIUM - EXPENDABLE GRATINGS
Comments: mercury as “starter” - heats up sodium vapor
Continuous spectrum due to atomic collisions
Absorption spectrum from cooler outer vapor
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Sodium Spectrum
Comment: Analog to Fraunhofer spectrum of sun - helium discovery
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Fraunhofer Absorption Spectrum
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BLACK
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Molecular Spectrum of I2
Comment on spectrum of H20 and CO2 and the Greenhouse Effect
ATOMIC PHYSICS PHENOMENA
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ATOMIC PHENOMENA LIST
FLUORESCENCE
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Black
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Fluorescein UV screen (using black light)
Comment: UV causes photoelectric effect
Electrons fall back to ground state emitting characteristic radiation
(page 4)
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P3-62 FLUORESCENT CHALK
Comment: Non-fluorescent
Colored in white light
White in white light
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P3-66 FLUORESCENT SOAP
Comment: Trick used to make clothes "whiter and brighter"
PHOSPHORESCENCE
Comment: Phosphorescence is "delayed" fluorescence
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P3-64 PHOSPHORESCENCE - BLACK LIGHT AND OSCILLOSCOPE
Comment: Useful in TV and computer monitors
APPLICATIONS
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Applications
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Black
LASERS
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P3-71 VISIBLE LASER
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HeNe Laser Drawing
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HeNe and LED Spectra
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Black
NEON SIGNS
Comment: color depends on gas and pressure
All "neon" signs aren't neon.
FLUORESCENT LIGHTS
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Cyclotron RF glow with inadequate vacuum
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Cyclotron Ion Source glow
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See you next time!
Pre-Show Demonstrations
P2-04 PHOTOELECTRIC PROPELLER
P2-06 PHOTOELECTRIC TRUCK
P3-61 FLUORESCENT LIQUIDS
P3-63 WAVELENGTH SHIFTER BAR
P3-64 PHOSPHORESCENCE - BLACK LIGHT AND OSCILLOSCOPE
P3-23 CATHODE-RAY TUBE - FLUORESCENCE EFFECT
DISCHARGE TUBES with Hand-Held Gratings
Hydrogen, Helium, Neon, Iodine
P3-71 VISIBLE LASER
Spectra of Light-Emitting Diodes
P3-01 PERIODIC CHART
P3-52 RESONANCE RADIATION
P2-11 INTERFERENCE OF PHOTONS
M1-11 LASER DIFFRACTION - FIXED DOUBLE SLITS
ELECTRON ORBITAL MODELS