two wire transmission
a power line isn't really 2 separate lines... it's all 1 line! connected by the load.
power --------------
| <= Load
|
ground -------------
ahh... impedence matching... no reflections? non-resonant.
-reacts to AC signals exactly the same way... ahh...
until get to end of wire, don't "know" that it isn't connected.
current flows as IF it is connected.
what if it wasn't this way? Then someone could disconnect the circuit a light-year away.
we should find out that he disconnected it... a light year later, right?
so, the light delay makes a difference. until we find out it isn't connected, the
circuit looks open.
a light bulb is like an antenna. turns electrical energy into... light! an EM wave.
so, think of a sine wave... amplitude modulation. how bright the light is.
light reflected by mirror -> radio waves reflected by metal!
if electric field FULLY parallel to conductor, then wave is not reflected... it is shorted
out. in essence, you made a receiving antenna. there are surface currents on the
conductor.
Huygen's principle: each point on a spherical wavefront is itself the source of a second
spherical wavefront. that's how we get waves behind a mountain or behind a building.
