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Bjarne
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How accurate is it possible to measure the EM spectre ?
FrankPlanck said:It depends on your tool...
russ_watters said:You're asking about the red and blue shift of stars and galaxies? Very accurately, since you have spectral absorption lines to compare with a reference.
Bjarne said:What about absorbed photons, is it only these that has very certain frequencies that are absorbed?
For example here http://www.astro.ucla.edu/~wright/doppler.htm is mentioned that those at 393 nm are absorbed.
My question is; - how accurate is that?
Is it only these that have the exact wavelength 393nm that are absorbed
What when one is 394 nm or 392nm , - will noting happen ?
If so it must be possible to measure much more accurate as 0.1% to 1%.
I mean the difference between 393nm and 392 nm is not much.
Bjarne said:What about absorbed photons, is it only these that has very certain frequencies that are absorbed?
For example here http://www.astro.ucla.edu/~wright/doppler.htm is mentioned that those at 393 nm are absorbed.
My question is; - how accurate is that?
Is it only these that have the exact wavelength 393nm that are absorbed
What when one is 394 nm or 392nm , - will noting happen ?
If so it must be possible to measure much more accurate as 0.1% to 1%.
I mean the difference between 393nm and 392 nm is not much.
Drakkith said:...spectrographs are looking at light that was emitted from an object. The spectral lines are absorbed at the SOURCE, not the instrument.
This would imply a velocity of ~1/400c or about 1000km/s, which is equivalent to a rotational period of about an hour for a sun-sized star. As comparison: The sun's surface needs 25-30 days for a rotation (depends on the latitude), and 1/400c is much more than the escape velocity of stars.Drakkith said:The light that is at 392 nm is NOT being absorbed by calcium, the line is wider than 1 nm because of several different effects, such as the rotation of the star.
"EM spectrum shift" refers to the change in the position of the electromagnetic spectrum for a specific wave frequency, such as red or blue light. This shift can occur due to various factors, including the motion of the source or observer, gravitational effects, or the Doppler effect.
The accuracy of EM spectrum shift is typically measured using spectroscopy techniques, which involve analyzing the frequencies of electromagnetic radiation emitted or absorbed by a substance. By comparing the observed frequencies to the known frequencies of the EM spectrum, the accuracy of the shift can be determined.
Measuring the accuracy of EM spectrum shift can provide valuable information about the source or observer of the electromagnetic radiation. It can also help in the detection of distant objects, such as stars and galaxies, as well as in understanding the behavior of light and other forms of electromagnetic radiation.
Red and blue light have different wavelengths and frequencies, which can lead to different shifts in the EM spectrum. For example, the red light emitted by a star may experience a larger shift due to the Doppler effect compared to the blue light emitted by the same star.
Some potential sources of error when measuring the accuracy of EM spectrum shift include instrumental limitations, atmospheric effects, and human error. For instance, the resolution of the spectroscopic instrument used may not be high enough to accurately measure small shifts, or atmospheric interference may affect the observed frequencies. Human error can also occur during data collection or analysis, leading to inaccurate measurements.