A
plane electromagnetic wave, with
wavelength 3.18 m, travels
in a free space in the
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Solution: Click For PDF Version (a)
Wavelength of
the plane electromagnetic wave
The frequency of the wave will be
(b) The amplitude of the electric field is
As the electric and magnetic fields for a plane wave are related as
the amplitude of the magnetic field will be
As the electric field is directed along the y axis, we have
As the wave
is travelling in the
will
be
From the property of the cross product we note that the magnetic field will be in the z direction. That is
(c) We recall
Therefore,
and
(d) Intensity of the wave
(e)
When the wave
falls normally upon a perfectly absorbing sheet of area
The radiation pressure exerted on the sheet will be
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direction with its electric vector
,
of amplitude
,
directed along the
axis. We
have to find (a) the
frequency of the wave; (b) the
direction and amplitude of the magnetic field associated with the
wave; (c) If
,
the values of
and
;
(d) the intensity of the wave;
and (e) assuming
that the wave falls upon a perfectly absorbing sheet of area
,
the rate with which the momentum is being
delivered to the sheet and the radiation pressure exerted on the
sheet.
.
.
,
.
.
,
. That is
.
.
.
,
