IT’S PHYSICS
PHYSICS IS PHUN – NOVEMBER 2007
S Welcome and Thanks
S Comment on origin of phrase “It’s Physics”
Q How does a magnifying glass work?
S “Use” magnifying glass like Sherlock Holmes
Use magnifying glass to start fire with sun’s rays
D L3-18 FOCUSING OF HEAT WAVES - OVERHEAD PROJECTOR
D L7-21 MAGNIFYING GLASS - TV
Comment: This is the “eyepiece” on a telescope or a microscope
Q Why does the pitch of a train whistle change as it passes you?
H1-52: AUDIOTAPE 82 MIN - SCIENCE OF SOUND - LONG VERSION
Section on Doppler Effect
Examples, Trains or gate clanging, beltway traffic
D H2-41 DOPPLER BALL
Rotate on string, the throw it
S Fraunhofer spectrum
Comment: Doppler shift in stars gives their speeds to establish Expanding Universe
(page 2)
Q Why do you produce an electric spark when you shuffle across a rug and touch metal?
S Quantum mechanical tunneling effect
"Sea" of electrons
Actually CONTACT, not FRICTION - rubbing increases contact
S Triboelectric series
D J1-01 TRIBOELECTRICITY - CHARGING BY FRICTION
S Van de Graaff explanation
S Another example of static electricity (charged babies)
CHARGING BY INDUCTION
D J1-11 ELECTROPHORUS
S Charging by Induction
Q What causes lightning?
Comment: Triboelectricity between air, water drops and ice crystals
S Origin of lightning - general overview
S Origin of lightning - various possibilities
S Origin of lightning - image and discharge points
S Origin of lightning - leader development
S Origin of lightning - main stroke
S Lightning striking tree - tree not damaged
S Shoes of man struck by lightning - man not hurt, only scared
D J2-03 VAN DE GRAAFF GENERATOR WITH GROUND SPHERE
D J1-24 ELECTROSTATIC HAIR RAISING
D J1-25 VAN DE GRAAFF - TRAINED RABBIT
Hare raising (ho, ho)
Q How does a lightning rod work?
D J2-14 LIGHTNING ROD SIMULATOR
Lightning rod may not DRAW lightning, but PREVENT it.
(page 3)
Q How does a microwave oven work?
Two concepts: absorption of waves by conducting materials
microwave standing waves
S Polar molecule Applet
D J4-12: ELECTROSTATIC FORCE - MOVING LUMBER
D G4-22 CHLADNI PLATES - OSCILLATOR DRIVEN
Story of Sophie Germain
S View of Microwave Oven
S Temperature in various parts of oven
Myth: Microwave oven cooks “from the inside out”
Danger: It can cook you - or animal - if inside oven
D J3-23: FARADAY CAGE - RADIOWAVES
S Superheating video
Q What are “Polaroid” sunglasses? How do they work
D K8-01 ELECTROMAGNETIC WAVE - MODEL
D M7-03 POLAROIDS AND GOOSENECK LAMP
D M7-17 REFLECTION OF LIGHT FROM DIELECTRIC AND CONDUCTOR
Comment: Light reflected from horizontal dielectric surface polarized horizontally
Examples: water, roads, especially wet roads
S Explanation
(page 4)
Q What makes a rainbow?
D N1-01 PRISMATIC SPECTRUM OF WHITE LIGHT - POINT SOURCE
D N1-41 RAINBOW - RAY MODEL
D N1-44 RAINBOW - OPTICAL BOARD
“Mie Scattering”
Primary bow at 42 deg, blue inside and red outside
S Primary rainbow, enhanced by use of polaroid filter
S Double Rainbow
S Double Rainbow #2
Secondary rainbow, 52 deg, red inside and blue outside
Comment: Glass bead angles 22 deg and 89 deg, due to greater refractive index
Q Why do stars “twinkle?’
D I2-43 CONVECTION - HOT PLATE
D E2-47 TWINKLING STAR
D E2-48 NON-TWINKLING PLANET
Stars are points, planets have relatively large size.
Q Why is the sky blue? Why is the sunset red?
S Re-phrase: Is the sky blue, or does it just look like it?
S Rayleigh scattering
Blue light scattered more than red as it passes through the atmosphere.
D M7-31 TYNDALL'S EXPERIMENT - COLLOIDAL SUNSET
Sulfur particles get larger and more numerous with time
3S Slides of sunrise taken from airplane (while colloid is working)
S TheEnd
PRE-SHOW DEMONSTRATIONS
J2-03 VAN DE GRAAFF GENERATOR WITH GROUND SPHERE
J1-24 ELECTROSTATIC HAIR RAISING
M7-17 REFLECTION OF LIGHT FROM DIELECTRIC AND CONDUCTOR
J1-03 KILOVOLT CARPET
M7-05 ROPE AND COOKIE COOLERS
M7-03 POLAROIDS AND GOOSENECK LAMP
EXTRA POLAROID SQUARES
N1-43 RAINBOW - GLASS BEAD MODEL
F4-31 SIPHON
F4-32 SIPHON - CHAIN MODEL
L3-31 GIANT MIRROR - CONCAVE AND CONVEX
L3-32 CYLINDRICAL MIRROR DEMONSTRATOR
L3-03 LARGE CONVEX MIRROR
L3-14 LARGE CONCAVE MIRROR
L2-05 PERVERTED IMAGE - AXES IN MIRROR
B1-07 DOUBLE CONE - SMALL
B1-11 BALANCE MAN
B1-12 CENTER OF MASS - HINGED STICK PARADOX
B1-13 CENTER OF MASS - FORK AND SPOON ON TOOTHPICK
B1-14 CENTER OF MASS - BOTTLE
B1-15 TOPPLING CYLINDERS