Links/Demos W14D2
Experiment:
We do an experiment using a spark gap antenna to generate radiation, a la Hertz. The preview
web submission is at
http://tsgphysics.mit.edu/sog/facWebSubmit.php?ssurvey=Microwaves
Movies and Links
Point Charge radiation applet:
http://web.mit.edu/viz/EM/simulations/radiationcharge.jnlp
Plane wave radiator applet:
http://peter-edx.99k.org/PlaneWave.html
Radiation pattern for quarter wave antenna (center to end of antenna is ¼ wavelength)
http://youtu.be/SV4kTSbFWRc or http://web.mit.edu/viz/EM/movies/light/hiResAntenna.avi
Microwave Interference (distant)
http://youtu.be/-O8V2QHkaLI or http://web.mit.edu/viz/EM/movies/light/distant.avi
Microwave Interference (close up) http://youtu.be/SkEdqP86hmU
http://web.mit.edu/viz/EM/movies/light/close.avi
or
Demonstrations
Microwaves
http://tsgphysics.mit.edu/front/?page=demo.php&letnum=Y 210&show=0
Interference of Microwaves
http://tsgphysics.mit.edu/front/?page=demo.php&letnum=P 4&show=0
Double Slit Interference w/Laser
http://tsgphysics.mit.edu/front/?page=demo.php&letnum=P 10&show=0
Polarization of Microwaves
http://tsgphysics.mit.edu/front/?page=demo.php&letnum=K 3&show=0
Polarization of Radio Waves (Dipole Antenna)
http://tsgphysics.mit.edu/front/?page=demo.php&letnum=K 4&show=0
Vibrating Spring (Hand Driven) spring will be a rubber tube
http://tsgphysics.mit.edu/front/?page=demo.php&letnum=C 35&show=0
Demonstration Description: Microwaves
http://tsgphysics.mit.edu/front/?page=demo.php&letnum=Y 210&show=0
OBJECTIVES
1. To observe the polarization and angular dependence of radiation from a microwave generator.
Demonstration Description: Interference of Microwaves
http://tsgphysics.mit.edu/front/?page=demo.php&letnum=P 4&show=0
A microwave transmitter emits a 10 GHz signal modulated by a 1000 Hz square wave from two
adjacent horns. A microwave receiver is placed facing the two sources and can be moved parallel
to their separation axis. The receiver is connected to an audio speaker to make the received
signal audible. With one of the transmitter horns covered, the receiver picks up maximum
amplitude when directly in front of the open horn. When both transmitter horns are uncovered,
however, the receiver picks up maximum amplitude when facing the center of the two horns,
thus demonstrating constructive interference. The received signal can also be displayed on an
oscilloscope.
Demonstration Description: Double Slit Interference w/Laser
http://tsgphysics.mit.edu/front/?page=demo.php&letnum=P 10&show=0
A laser is directed at a Cornell "Slitfilm demonstrator" slide containing double slits of different
widths and spacings, and the resulting diffraction patterns are observed on a screen.
Video:
http://techtv.mit.edu/videos/2384-laser-diffraction-and-interference
Demonstration Description: Polarization of Microwaves
http://tsgphysics.mit.edu/front/?page=demo.php&letnum=K 3&show=0
A microwave transmitter emits a 10 GHz polarized signal modulated by a 1000 Hz square wave.
A receiver, connected to an audio speaker to make the received signal audible, faces the
transmitter. A metallic grid, consisting of thin and closely spaced parallel bars, is held between
them at various orientations. When the bars are held parallel to the E-field, the signal is blocked.
When the bars are rotated 900, however, the signal is uninterrupted. A solid metallic sheet
attenuates the waves. The output can also be displayed on an oscilloscope.
Video:
http://techtv.mit.edu/videos/752-mit-physics-demo-microwave-polarization
Demonstration Description: Polarization of Radio Waves (Dipole Antenna)
http://tsgphysics.mit.edu/front/?page=demo.php&letnum=K 4&show=0
A 4-meter RF oscillator (~80 MHz) is used with a dipole antenna to show polarization and
standing waves. A small lamp at the center of the dipole glows brightly with the antenna is held
at anti-node points parallel to the transmitter. If the antenna is rotated so that it lies perpendicular
to the transmitting antenna, the bulb goes out.
Video:
http://techtv.mit.edu/videos/796-mit-physics-demo-dipole-antenna
Demonstration Description: Vibrating Spring (Hand Driven) spring will be a rubber tube
http://tsgphysics.mit.edu/front/?page=demo.php&letnum=C 35&show=0
A long spring, clamped or held by a student at one end, is hand-driven by the demonstrator at its
other end. The higher the driving frequency achieved, the more nodes are observed along the
spring.