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Doppler Caused By Differential Between
Speeds
If the speed of light is a constant, the Doppler
Effect in light cannot exist or the need arises for a completely different
explanation of how the Doppler Effect works in light. It must be arbitrarily
constructed simply to support assumptions of
relativity.
A better understanding of of the underlying cause of frequency is one of the prerequisites
for a deep understanding of the Doppler Effect.
To put it in simplistic terms, one of the causes of frequency is the
relationship between the initial force applied to the medium and the elasticity,
or 'reactiveness' of the medium, the other is just the speed at which the
emitter itself is vibrating. This difference could be exemplified in
the difference between a tuning fork and a firecracker. The tuning fork's
vibration is faithfully transmitted into the surrounding air whereas
the sound of a firecracker is caused entirely by the compression of
the media. Amplitude is also involved with compressing the media because
the more force applied to the media before it can react, the higher the
amplitude will be.
Below is a visual representation of
frequency to establish a baseline for the following visual explanations of
the Doppler Effect. What you see here is the relation between frequency
and wavelength.
Below we
have an example of Doppler Effect caused by a stationary sound source and a
moving listener. (Note that stationary vs moving is determined by the
medium)
In this
example, though the sound was inscribed on the medium at a frequency of
100, the listener was moving so therefore the wave appears to be a shorter
wavelength (higher frequency) than we know it to be because our
perspective is the same as the medium. The listener simply traversed more
waves during the measuring period than he would have if he remained
still.
Note that if
the moving listener above measured the speed of sound from his
perspective it would be measured as 680.58 m/s.
In this
example we have the Doppler Effect caused by a moving emitter (in relation
to the medium). In this example, the medium itself is inscribed with a
higher frequency sound. What is happening is that the speed at which a
single wavefront can escape from the emitter is slower now in comparison
to the Jet's (emitter's) speed. A single wave is only able to travel half as far away
from the emitter before another wave is inscribed into the medium.
Therefore the wavelength is half as long, the frequency is
increased.
In the final example above
you can see that the speed of the emitter has overcome the ability of the
medium to transmit the sound. The jet passes right through a wavefront
as it inscribes it. The compressed area just can't get out of the
way fast enough. What you can see is that the speed of
sound is actually a property of the medium. It describes its
elasticity. It describes how quickly compressed air can normalize itself
back to its original pressure by re-distributing the pressure into the
surrounding air.
Note that the
final example is just a thought experiment because the air is so disturbed
around something traveling that speed that there are many more
considerations than we need to get into.
Summary
Doppler, red/blue shift, frequency change, and wavelength
change -whatever- caused by motion happens by one of two
mechanisms:
1) The listener traverses additional waves during the test period
because the speed of sound relative to the listener is
greater.
2) The individual waves escaping from the emitter cannot get as far
away from the emitter before the next wave is produced because of the
difference between the emitter's speed and the speed of sound.
(elasticity/reaction speed of the medium) The speed of sound is measured
to be the same to the listener in this case though.
Without a medium and with the speed of light always constant,
neither of these conditions can be met to cause a reduction or increase in
wavelength in light. The only explanations of light Doppler cannot go
to the same depth of explanation. The simplistic notion that the wave has
more or less energy based on the shift is severely lacking depth. It is a
description instead of an explanation. The actual mechanism of the
wavelength change cannot be explained in this illogical
view.
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