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Date: Apr 26, 2008 18:06
What I am going to do is use sound to measure the doppler shift of light.
This is the set up.
S is a monochromatic light source, emitting light of frequency 7.5E14 hz (FL).
For every 7E14 cycles of that light, the source emits a short beep of sound.
The Beep frequency is 1 second.
A detector at rest with the source and some distance away counts the beeps and
correctly calculates the frequency of the emitted light to be FL.
Next, the detector is set in motion towards the source at half the velocity of
sound. The received beep frequency increases to double its previous value, ie.,
to 2Fs.
This implies that the detector is now receiving twice the number of light
cycles per second as it did when at rest. In other words the light appears to
have been doppler shifted to double its frequency in the source frame.
Q) What is the colour of the light seen by an observer moving with the
detector?
Henri Wilson. ASTC,BSc,DSc(T)
www.users.bigpond.com/hewn/index.htm
....specialising in teaching physics to engineers and mathematicians....
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Author: YBMYBM Date: Apr 26, 2008 18:19
Dr. Henri Wilson wrote:
> What I am going to do is use sound to measure the doppler shift of light.
Ralph Rabbidge, you're not even able to go to bathroom alone...
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Author: DonoDono Date: Apr 26, 2008 18:21
On Apr 26, 6:25 pm, YBM wrote:
> Dr. Henri Wilson wrote:
>> What I am going to do is use sound to measure the doppler shift of light.
>
> Ralph Rabbidge, you're not even able to go to bathroom alone...
:-) :-)
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Author: rbwinnrbwinn Date: Apr 27, 2008 07:31
On Apr 26, 6:06�pm, HW@....(Dr. Henri Wilson) wrote:
> What I am going to do is use sound to measure the doppler shift of light.
>
> This is the set up.
>
> S is a monochromatic light source, emitting light of frequency 7.5E14 hz (FL).
>
> For every 7E14 cycles of that light, the source emits a short beep of sound.
> The Beep frequency is 1 second.
>
> A detector at rest with the source and some distance away counts the beeps and
> correctly calculates the frequency of the emitted light to be FL.
>
> Next, the detector is set in motion towards the source at half the velocity of
> sound. The received beep frequency increases to double its previous value, ie.,
> to 2Fs.
>
> This implies that the detector is now receiving twice the number of light
> cycles per second as it did when at rest. In other words the light appears to
> have been doppler shifted to double its frequency in the source frame. ...
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Author: Tom RobertsTom Roberts Date: Apr 27, 2008 09:03
rbwinn wrote:
> The speed of sound is only 1,087 feet per second. Half of that would
> only be 543.5 feet per second. That is not fast enough to change the
> frequency of the light enough to worry about.
Sure it is! This is how police radar and laser guns measure the speed of
traffic, and they do so for motions ~100 times smaller. A laboratory
instrument could measure speed thousands of times better than that.
(Henri's "riddle" is utterly ridiculous, and shows how deep are his
misunderstandings of very basic physics.)
Tom Roberts
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Date: Apr 27, 2008 15:09
On Sun, 27 Apr 2008 07:31:45 -0700 (PDT), rbwinn juno.com> wrote:
>On Apr 26, 6:06?pm, HW@....(Dr. Henri Wilson) wrote:
>> What I am going to do is use sound to measure the doppler shift of light.
>>
>> This is the set up.
>>
>> S is a monochromatic light source, emitting...
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Author: rbwinnrbwinn Date: Apr 27, 2008 17:24
On Apr 27, 9:03�am, Tom Roberts sbcglobal.net> wrote:> rbwinn wrote:
>> The speed of sound is only 1,087 feet per second. �Half of that would
>> only be 543.5 feet per second. �That is not fast enough to change the
>> frequency of the light enough to worry about.
>
> Sure it is! This is how police radar and laser guns measure the speed of
> traffic, and they do so for motions ~100 times smaller. A laboratory
> instrument could measure speed thousands of times better than that.
>
> (Henri's "riddle" is utterly ridiculous, and shows how deep are his
> misunderstandings of very basic physics.)
>
> Tom Roberts
Radar does not change frequency. It is reflected from a target at the
same frequency it had before.
Robert B. Winn
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Author: Bryan OlsonBryan Olson Date: Apr 27, 2008 18:16
rbwinn wrote:
> Tom Roberts wrote:
>> rbwinn wrote:
>>> The speed of sound is only 1,087 feet per second. �Half of that would
>>> only be 543.5 feet per second. �That is not fast enough to change the
>>> frequency of the light enough to worry about.
>> Sure it is! This is how police radar and laser guns measure the speed of
>> traffic, and they do so for motions ~100 times smaller. A laboratory
>> instrument could measure speed thousands of times better than that.
>
> Radar does not change frequency. It is reflected from a target at the
> same frequency it had before.
Dude, just look it up.
--
--Bryan
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Author: rbwinnrbwinn Date: Apr 27, 2008 22:32
On Apr 27, 6:16Â pm, Bryan Olson nowhere.org> wrote:> rbwinn wrote:
>> Tom Roberts wrote:
>>> rbwinn wrote:
>>>> The speed of sound is only 1,087 feet per second. �Half of that would
>>>> only be 543.5 feet per second. �That is not fast enough to change the
>>>> frequency of the light enough to worry about.
>>> Sure it is! This is how police radar and laser guns measure the speed of
>>> traffic, and they do so for motions ~100 times smaller. A laboratory
>>> instrument could measure speed thousands of times better than that.
>
>> Radar does not change frequency. Â It is reflected from a target at the
>> same frequency it had before.
>
> Dude, just look it up.
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Author: Bryan OlsonBryan Olson Date: Apr 28, 2008 00:30
rbwinn wrote:
> Bryan Olson wrote:
>> rbwinn wrote:
>>> Tom Roberts wrote:
>>>> rbwinn wrote:
>>>>> The speed of sound is only 1,087 feet per second. �Half of that would
>>>>> only be 543.5 feet per second. �That is not fast enough to change the
>>>>> frequency of the light enough to worry about.
>>>> Sure it is! This is how police radar and laser guns measure the speed of
>>>> traffic, and they do so for motions ~100 times smaller. A laboratory
>>>> instrument could measure speed thousands of times better than that.
>>> Radar does not change frequency. It is reflected from a target at the
>>> same frequency it had before.
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