文档介绍：Kottan-labs 5/20/2002
Introduction in Optics I:
I-1) Electro-ic Waves
The discussion of electric and ic fields can be classified in two
general categories. The first includes fields that do not vary with time. The
electrostatic field of a distribution of charges at rest and the ic field of
a steady current in a conductor are examples of fields, which, while they
may vary from point to point in space, do not vary with time at any
individual point. For such situations it is possible to treat the electric field
and ic fields independently, without worrying about interactions
between the fields.
The second category includes situation in which the fields do vary
with time, and in all such cases it is not possible to treat the fields
independently. Faraday’s law tells us that a time-varying ic field acts
as source of electric field. This field is manifested in the induced
electromotive forces (emf’s) in inductances and transformers. Similarly, in
developing the general formulation of Ampere’s law, which is valid for
charging capacitors and similar situations as well as for ordinary conductors,
we found it necessary to regard a changing electric field as a source of
ic field. Therefore, when either field is changing with time, a field of
the other kind is induced in adjacent regions of space. We are led to consider
the possibility of an ic disturbance, consisting of time-varying
electric and ic fields, which can propagate through space from one
region to another, even when there is no matter in the intervening region.
Such a disturbance, if it exists will have the properties of a wave, and the
appropriate descriptive term is ic wave. Such waves do exist;
radio and television transmission, x-ray and in the current context most
important: light. Figure I-1-1 visualizes such ic wave
propagation.
y
x
z
Figure I-1-1: ic monochromatic wave. E and B correspond to
the electric and ic field. Note the transverse character of the wave.
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