In P Chem experiment: Balmer Spectra of Atomic Hydrogen. lab manual link I post

Question

In P Chem experiment: Balmer Spectra of Atomic Hydrogen. lab manual link I post here, if you don't know what I am talking about https://chem.libretexts.org/LibreTexts/University_of_California_Davis/UCD_Chem_105/UCD_Chem_105%3A_Lab_Manual/Lab_6%3A_Atomic_Hydrogen_Spectroscopy my question is : How does the bandwidth or resolution of your spectrum correlate with the slit width? Approximately and exactly? Can you calculate the inverse linear dispersion for the monochromator in this instrument?Your spectrum will contain both the hydrogen lines and the intense lines from the referencesource. You can use these as an internal reference. How can you best determine which lines are fromthe reference source?

can you type for the answer. hand writing sometime is hard to read thx.

Explanation / Answer

Increased slit width gives you an averaging effect i.e., if you take a spectra and average it over few data points then the same effect would be obtained by recording the spectra with increasing slit width.

Also, as the slit width increases, the band width also increases i.e., you end up exciting with a larger range of wavelengths of light.

Linear dispersion defines the extent to which a spectral interval is spread out across the focal field of a spectrometer and is expressed in nm/mm, Å/mm, cm-1/mm, etc. For example, consider two spectrometers: one instrument disperses a 0.1 nm spectral segment over 1 mm while the other takes a 10 nm spectral segment and spreads it over 1 mm.

It is easy to imagine that fine spectral detail would be more easily identified in the first instrument than the second. The second instrument demonstrates "low" dispersion compared to the "higher" dispersion of the first. Linear dispersion is associated with an instrument's ability to resolve fine spectral detail.

Linear dispersion perpendicular to the diffracted beam at a central wavelength, , is given by:

nm/mm

Normally, we use the “reciprocal linear dispersion”, which gives the wavelength dispersion in nm/mm of slit width.

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