Transcript Slides

Upcoming Classes
Tuesday, Nov. 6th
Second Set of Oral Presentations
Assignment due: Presentation or paper
Thursday, Nov. 8th
Smoke and Mirrors
Assignment due:
* Read “Optics and Realism in Renaissance Art”, Scientific
American, Dec. 2004
NOTE: This paper is not in your course reader; you need to
find it in the library.
Upcoming Deadlines
Tuesday, November 6th
Second Set of Oral Presentations
Second term paper (if not presenting)
Tuesday, November 15th
Outline of third oral presentation or written
paper
Oral Presentations (II)
The following persons will give oral presentations
on Tuesday, November 6th :
• Luttrell,Katherine
• Macdonald,Keith
• McDonald,Kathleen
• Mendoza,Jazmin
• Nguyen,Jennifer
• Nguyen,Linda
For everyone else, term paper is due on that date.
Oral Presentations (III)
The following persons will give oral presentations
on Tuesday, December 4th :
•
•
•
•
•
Remmel, Katherine
Sugiura, Ayuka
Yamaguchi, Asuka
Zeber, Emily,
Dinh, Phiphi
For everyone else, term paper is due on that date.
Homework 5: Exploratorium
Located near Golden Gate Bridge.
Extra Credit: Beethoven Center
Visit the Beethoven
Center on the Fifth floor
of MLK library.
Take a photo of yourself
with one of the pianos
or harpsichords.
Turn in photo by Thurs.,
Nov. 11th for one quiz
worth of extra credit.
Extra Credit: San Jose Ballet
See a performance of San Jose Ballet in San Jose
Center for Performing Arts (Nov. 15th – 18th ).
Turn in your ticket receipt. Worth one homework
assignment or three quiz/participation credits.
Ramon Moreno in CARMINA BURANA
Brian Holmes, Composer
Professor Brian Holmes is a composer
and professional French Horn player.
He also has a Ph.D. in Physics and
teaches in both the Music and Physics
departments at SJSU.
Extra Credit: Concert at Petit Trianon
See the premier performance of Brian Holmes’
Death's Jest-Book Overture by the Mission
Chamber Orchestra on Sat., Nov. 3rd, 7:30pm.
Turn in your ticket receipt (student tickets are $17).
Worth two quiz/participation credits.
Le Petit Trianon, 72 N. 5th St., San Jose
Radio &
Television
(& Microwaves
& X-rays)
Electromagnetic Waves
Moving charges (currents) create magnetic fields.
Oscillating magnetic fields create electric fields.
These effects create electromagnetic waves.
Demo: Magnetic Force & Current
Moving charges in an electric current
experience a force due to magnetic field.
Magnetic Force on Charges
Moving electric charges deflected by
magnetic fields.
Demo: Crooke’s Tube
Electron beam in a Crooke’s tube is deflected
when a magnet is brought near the tube.
Television Tube
Electron beams, deflected by magnetic
fields, are used to create TV images.
Electromagnets
Demo: Magnets & TV sets
Picture on a TV set is distorted by presence of a
magnet since picture formed by an electron beam.
Demo: Electromagnetic Oscillations
Put alternating current into an
electromagnet and you create
an oscillating magnetic field.
This oscillating magnetic field
induces electrical currents by
inducing electrical field
oscillations.
This is, effectively, a very low
frequency electromagnetic
antenna.
Coil with bulb
Oscillating
Magnetic
Field
ElectroMagnet
Connect to
alternating
current (AC)
Electromagnetic Spectrum
Cell phone
Very broad spectrum of
electromagnetic waves
Speed of Light
Speed of light is 300,000,000 m/s
Since
(Wave Speed)
(Wavelength) =
(Frequency)
then radio station at 100 Megahertz has
300,000,000 m/s
(Wavelength) =
= 3 meters
100,000,000 Hz
Demo: Light & Sound
Sound waves can only travel
through a material, such as
air, but light waves can
travel through vacuum.
Can see cell phone
ringing inside vacuum
chamber but don’t hear
the sound.
Sound waves are not electromagnetic waves
Transparent & Opaque Materials
A material is transparent or
opaque to different
wavelengths depending
on its atomic properties.
Some opaque materials
absorb certain waves
while other materials
reflect those electromagnetic waves.
For visible light, glass is
transparent, while rubber
and metal are opaque
(rubber absorbs,
metal reflects)
Demo: Microwaves
Test transparency, opacity, & reflectivity of:
• Metal (aluminum foil)
• Wood (book)
Microwave
Microwave
• Glass
Receiver
Transmitter
• Water
Wavelength of microwaves
is fraction of a centimeter
(longer than visible light).
Demo: Ultraviolet Light
Fluorescent (Day-Glo) paint converts
invisible ultraviolet light into visible light.
Test opacity of:
• Glass
• Water
• Sunscreen
Wavelength of ultraviolet light
is about the size of bacteria
(shorter than visible light).
Ultraviolet
Lamp
Fluorescence
Some materials, such as fluorite, absorb
invisible ultraviolet radiation and re-emit
the electromagnetic energy as visible light.
Fluorescent
bulbs have a
phosphor
coating
Television screen is fluorescent screen
Check Yourself
The forced oscillations of ultraviolet light
happen to match the natural frequency of
electrons in glass. So what happens?
Resonance occurs, causing the light’s energy
to be absorbed by the electrons.
So is glass opaque to ultraviolet light?
Yes, and glass is transparent to visible light
since its wavelength is lower. Sunglasses
(tinted or untinted) protect your eyes from
UV (ultraviolet) light while letting you see.
Incandescent Radiation
All objects radiate light;
higher the temperature
the higher the
frequency.
At room temperature the
radiated light is at
frequencies in the
infrared, too low for our
eyes to see.
Special cameras are
sensitive to this infrared
radiation.
75º
98º
Attics in this house were kept warm
for growing marijuana.
Demo: Infrared Light
Digital cameras, such as in cell phones, are
sensitive to infrared light, such as from a
remote control or any hot object.
Microwave
Transmitter
Microwave
Receiver
Next Lecture
Second Round of
Oral Presentations
Remember:
Assignment due:
Presentation or term paper due.
Quiz after presentations