14 RadioTV

Upcoming Classes: 

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: 

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): 

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): 

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: 

Homework 5: Exploratorium Located near Golden Gate Bridge.

Extra Credit: Beethoven Center: 

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: 

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: 

Brian Holmes, Composer

Extra Credit: Concert at Petit Trianon: 

Extra Credit: Concert at Petit Trianon Le Petit Trianon, 72 N. 5th St., San Jose 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.

Radio & Television (& Microwaves & X-rays) : 

Radio & Television (& Microwaves & X-rays)

Electromagnetic Waves: 

Electromagnetic Waves Moving charges (currents) create magnetic fields. Oscillating magnetic fields create electric fields. These effects create electromagnetic waves.

Demo: Magnetic Force & Current: 

Demo: Magnetic Force & Current Moving charges in an electric current experience a force due to magnetic field.

Magnetic Force on Charges: 

Magnetic Force on Charges Moving electric charges deflected by magnetic fields.

Demo: Crooke’s Tube: 

Demo: Crooke’s Tube Electron beam in a Crooke’s tube is deflected when a magnet is brought near the tube.

Television Tube: 

Television Tube Electron beams, deflected by magnetic fields, are used to create TV images. Electromagnets

Demo: Magnets & TV sets: 

Demo: Magnets & TV sets N S Picture on a TV set is distorted by presence of a magnet since picture formed by an electron beam.

Demo: Electromagnetic Oscillations: 

Demo: Electromagnetic Oscillations Connect to alternating current (AC) Oscillating Magnetic Field Electro- Magnet 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

Electromagnetic Spectrum: 

Electromagnetic Spectrum Very broad spectrum of electromagnetic waves Cell phone

Speed of Light: 

Speed of Light Speed of light is 300,000,000 m/s Since (Wavelength) = then radio station at 100 Megahertz has (Wavelength) = = 3 meters (Wave Speed) (Frequency) 300,000,000 m/s 100,000,000 Hz

Demo: Light & Sound: 

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 Radio Wave

Transparent & Opaque Materials: 

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 electro-magnetic waves. For visible light, glass is transparent, while rubber and metal are opaque (rubber absorbs, metal reflects)

Demo: Microwaves: 

Demo: Microwaves Test transparency, opacity, & reflectivity of: Metal (aluminum foil) Wood (book) Glass Water Microwave Transmitter Microwave Receiver Wavelength of microwaves is fraction of a centimeter (longer than visible light).

Demo: Ultraviolet Light: 

Demo: Ultraviolet Light Fluorescent (Day-Glo) paint converts invisible ultraviolet light into visible light. Test opacity of: Glass Water Sunscreen Ultraviolet Lamp Wavelength of ultraviolet light is about the size of bacteria (shorter than visible light).

Fluorescence : 

Fluorescence Some materials, such as fluorite, absorb invisible ultraviolet radiation and re-emit the electromagnetic energy as visible light. Television screen is fluorescent screen Fluorescent bulbs have a phosphor coating

Check Yourself: 

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: 

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. Attics in this house were kept warm for growing marijuana. 98º 75º

Demo: Infrared Light: 

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 : 

Next Lecture Second Round of Oral Presentations Remember: Assignment due: Presentation or term paper due. Quiz after presentations