Calibrating the Spectroscope
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The calibration of your spectroscope is necessary to correct for
systematic error. This is done by comparing your
experimentally- determined wavelengths to wavelengths obtained from
the literature. A convenient source of emission lines is the helium
discharge tube.
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Proceed to the station with the helium tube in the power supply.
Look through the eyepiece of your spectroscope and find the six
helium lines. Note the position of these lines with regard to the
scale and record their colors and their wavelengths in Angstroms
in your laboratory notebook.
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Readings are dependent on the position of your eye. Therefore,
one person should take the readings and should be consistent with
the position of their eye relative to the eyepiece.
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Prepare a calibration plot by graphing the scale reading obtained
experimentally on the x axis versus the literature wavelength value
on the y axis. You should use a full sheet of paper for the plot.
This plot will be used to calculate the corrected wavelengths for
the hydrogen spectrum and will be different for each spectroscope.
Therefore, take data carefully and use your own, not another group's!
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Color of Line |
Theoretical Wavelength in Angstroms |
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Blue-violet |
4471 |
Blue |
4713 |
Green |
5015 |
Orange |
5875 |
Red-Orange |
7065 |
Dark Red |
7281 |
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Here is an example of what a calibration graph looks like.
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Experimental vs. Theoretical Wavelengths |
4471 |
4450 |
4713 |
4700 |
5015 |
5000 |
5875 |
5860 |
7065 |
7040 |
7281 |
7250 |
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