THE ATOM
PHYSICS IS PHUN - January 2008
SPlease take a grating
SPlease be Seated
SProgram 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
SThe Elements, by Tom Lehrer
ELECTROMAGNETIC SPECTRUM
DK8-01 ELECTROMAGNETIC WAVE - MODEL
Comment: Variety of EM waves - all obey the equation
Sc = f
SEM Spectrum by frequency, wavelength, and photon energy (neglect now)
DN1-05 SPECTRA - VISIBLE AND INVISIBLE
Comment: UV using fluorescein dye, IR using thermocouple
SDuality of Light
Comment: photon behavior of light/EM waves - great paradox of physics
SE=hf (NOTE: Einstein Nobel Prize for this)
SBoiling Water and the Photoelectric Effect
DP2-02 PHOTOELECTRIC EFFECT IN ZINC - ARC LAMP
SEM Spectrum by frequency, wavelength, and photon energy
DP2-05 PHOTO-RESISTOR RELAY
Comment: operates street lamps using photoelectric effect
Examples: photoelectric calculators, experimental car (UM)
(page 2)
ATOMIC STRUCTURE AND TRANSITIONS
SAtomic 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
DP3-53 ATOMIC ENERGY LEVEL MODEL
Comment: Higher level is less strongly bound, larger electron radius
SPeriodic 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
SAtomic Spectra – list ones to be seen here
SBlack
DDiffraction spectrum of white light with gratings
DP3-51 BALMER SERIES with TV
SHydrogen atomic transitions
Comments: n=1 series UV (Lyman)
N=2 series (Balmer) visible
N=3 series IR (Paschen)
SBlack
(page 3)
DN2-02 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.
DN2-03 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
SSodium Spectrum
Comment:Analog to Fraunhofer spectrum of sun - helium discovery
SFraunhofer Absorption Spectrum
SBLACK
DMolecular Spectrum of I2
Comment on spectrum of H20 and CO2 and the Greenhouse Effect
ATOMIC PHYSICS PHENOMENA
SATOMIC PHENOMENA LIST
FLUORESCENCE
SBlack
DFluorescein UV screen (using black light)
Comment:UV causes photoelectric effect
Electrons fall back to ground state emitting characteristic radiation
(page 4)
DP3-62 FLUORESCENT CHALK
Comment:Non-fluorescent
Colored in white light
White in white light
DP3-66 FLUORESCENT SOAP
Comment: Trick used to make clothes "whiter and brighter"
PHOSPHORESCENCE
Comment: Phosphorescence is "delayed" fluorescence
DP3-64 PHOSPHORESCENCE - BLACK LIGHT AND OSCILLOSCOPE
Comment: Useful in TV and computer monitors
APPLICATIONS
SApplications
SBlack
LASERS
DP3-71 VISIBLE LASER
SHeNe Laser Drawing
SHeNe and LED Spectra
SBlack
NEON SIGNS
Comment: color depends on gas and pressure
All "neon" signs aren't neon.
FLUORESCENT LIGHTS
SCyclotron RF glow with inadequate vacuum
SCyclotron Ion Source glow
SSee 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