THE ATOM
PHYSICS IS PHUN - January 2008
S Please take a grating
S Please be Seated
S 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
S The Elements, by Tom Lehrer
ELECTROMAGNETIC SPECTRUM
D K8-01 ELECTROMAGNETIC WAVE - MODEL
Comment: Variety of EM waves - all obey the equation
S c=f
S EM Spectrum by frequency, wavelength, and photon energy (neglect now)
D N1-05 SPECTRA - VISIBLE AND INVISIBLE
Comment: UV using fluorescein dye, IR using thermocouple
S Duality of Light
Comment: photon behavior of light/EM waves - great paradox of physics
S E=hf (NOTE: Einstein Nobel Prize for this)
S Boiling Water and the Photoelectric Effect
D P2-02 PHOTOELECTRIC EFFECT IN ZINC - ARC LAMP
S EM Spectrum by frequency, wavelength, and photon energy
D P2-05 PHOTO-RESISTOR RELAY
Comment: operates street lamps using photoelectric effect
Examples: photoelectric calculators, experimental car (UM)
(page 2)
ATOMIC STRUCTURE AND TRANSITIONS
S 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
D P3-53 ATOMIC ENERGY LEVEL MODEL
Comment: Higher level is less strongly bound, larger electron radius
S 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
S Atomic Spectra – list ones to be seen here
S Black
D Diffraction spectrum of white light with gratings
D P3-51 BALMER SERIES with TV
S Hydrogen atomic transitions
Comments: n=1 series UV (Lyman)
N=2 series (Balmer) visible
N=3 series IR (Paschen)
S Black
(page 3)
D 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.
D 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
S Sodium Spectrum
Comment: Analog to Fraunhofer spectrum of sun - helium discovery
S Fraunhofer Absorption Spectrum
S BLACK
D Molecular Spectrum of I2
Comment on spectrum of H20 and CO2 and the Greenhouse Effect
ATOMIC PHYSICS PHENOMENA
S ATOMIC PHENOMENA LIST
FLUORESCENCE
S Black
D Fluorescein UV screen (using black light)
Comment: UV causes photoelectric effect
Electrons fall back to ground state emitting characteristic radiation
(page 4)
D P3-62 FLUORESCENT CHALK
Comment: Non-fluorescent
Colored in white light
White in white light
D P3-66 FLUORESCENT SOAP
Comment: Trick used to make clothes "whiter and brighter"
PHOSPHORESCENCE
Comment: Phosphorescence is "delayed" fluorescence
D P3-64 PHOSPHORESCENCE - BLACK LIGHT AND OSCILLOSCOPE
Comment: Useful in TV and computer monitors
APPLICATIONS
S Applications
S Black
LASERS
D P3-71 VISIBLE LASER
S HeNe Laser Drawing
S HeNe and LED Spectra
S Black
NEON SIGNS
Comment: color depends on gas and pressure
All "neon" signs aren't neon.
FLUORESCENT LIGHTS
S Cyclotron RF glow with inadequate vacuum
S Cyclotron Ion Source glow
S 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