Download Class #34 Slides

4/12/06
Poster Session Meetings
Electromagnetic Waves and Radio
•Schedule appointment
•Change/Modify your topic
•Plan your poster
Friday’s Reading:
•Etc.
•Section 13.2: Microwave Ovens (pp. 432 – 438)
Upcoming Reading Assignments:
•Section 14.1: Sunlight (pp. 445 – 453)
•Section 14.2: Discharge Lamps (pp. 454 – 463)
•Section 14.3: Lasers and LEDs (pp. 464 – 470)
•Section 15.1: Cameras (pp. 478 – 488)
•Section 15.2: Optical Recording and Communication (pp. 489 – 497)
Types of Memory
•
Magnetic (information stored in orientation of poles)
•
Flash (information stored in charge on transistor’s
“floating gates”)
•
Optical (discuss later in course)
Electric and Magnetic Fields
Sources of Electric Field?
Accelerated Charges
Sources of Magnetic Field?
Electromagnetic Waves & Electromagnetic Spectrum
Exercise: Visible light is a small portion of the
electromagnetic spectrum. The wavelengths of
visible light range from 400 nm (violet) to about
780 nm (red). What is the range of frequencies of
visible light? (1 nm = 10-9 m)
Figure from Tipler & Mosca,
“Physics for Scientists and Engineers”,
5th edition, p. 977
Direction of EM Waves & Polarization
EM wave made up of
Electric field and Magnetic field
E perpendicular to B
Direction of wave perpendicular to E and B
 

E B  v
Exercise: The Electric field part of an EM
wave oscillates IN and OUT of the screen.
What are possible directions of the
Magnetic field part of this EM wave?
Follow-up Exercise: An EM wave is moving
to the LEFT. At some instant at some point,
the Electric field points OUT of the screen.
At this instant at this point, what is the
direction of the Magnetic field?
Making a Radio Wave