Download Microwaves

The following shows the existence of oscillating magnetic
and electric fields in an electromagnetic wave
The detection of the fields relies on the two properties:
1. Ed = V (electric field drives a current back and forth in the
antenna)
2. ∆фB /∆t = V (driving a current back and forth around the loop)
The sensor is at right
angles to the antenna.
Little electric field is
detected.
ANTENNA
Diode
dipole
dipole
Antenna
Diode
SENSOR
Antenna
Meter
Dipole
Diode
Dipole
Dipole
The sensor antenna is parallel
to the plane of the electric field.
The electric field makes a larger
current through the sensor
antenna.
As the electric field passes the wire it forces electrons up and down
generating heat. The energy must come from the field and
therefore the amplitude of the electric field and the magnetic
field are reduced.
wire
The alternating magnetic field produces the alternating electric field.
The alternating electric field produces an alternating magnetic field.
meter
LOOP
diode
B
The plane of the magnetic field is horizontal and parallel to
the plane of the sensor loop. Therefore no magnetic flux
goes through the loop and the magnetic field of the
electromagnetic wave is not sensed.
The magnetic field now passes
through the loop generating a
larger current through the meter
in the sensor circuit.
diode
Click on the movie square and see what
happens when this screen is lowered
between the sensor and the antenna.
Click on the movie and
watch what happens to the
electromagnetic wave
field…as measured by
sampling the electric field…
when horizontal rods are
placed between the sensor
and the generated field.
Energy is not absorbed by the rods because the vertically
polarized electric field only moves electrons across the
diameter of the rods and therefore does not generate
large currents and thermal energy and does not get
absorbed.