Editing Ultraviolet–visible spectroscopy (section)

====Spectral bandwidth====
Spectral bandwidth of a spectrophotometer is the range of wavelengths that the instrument transmits through a sample at a given time.<ref>{{Cite web |title=Persee PG Scientific Inc. – New-UV FAQ: Spectral Band Width |url=http://www.perseena.com/index/newsinfo/c_id/37/n_id/7.html |archive-url=https://web.archive.org/web/20180921065923/http://www.perseena.com/index/newsinfo/c_id/37/n_id/7.html |url-status=usurped |archive-date=21 September 2018 |access-date= |website=www.perseena.com}}</ref> It is determined by the light source, the [[monochromator]], its physical slit-width and optical dispersion and the detector of the spectrophotometer. The spectral bandwidth affects the resolution and accuracy of the measurement. A narrower spectral bandwidth provides higher resolution and accuracy, but also requires more time and energy to scan the entire spectrum. A wider spectral bandwidth allows for faster and easier scanning, but may result in lower resolution and accuracy, especially for samples with overlapping absorption peaks. Therefore, choosing an appropriate spectral bandwidth is important for obtaining reliable and precise results.

It is important to have a monochromatic source of radiation for the light incident on the sample cell to enhance the linearity of the response.<ref name="dev" /> The closer the bandwidth is to be monochromatic (transmitting unit of wavelength) the more linear will be the response. The spectral bandwidth is measured as the number of wavelengths transmitted at half the maximum intensity of the light leaving the monochromator. 

The best spectral [[bandwidth (signal processing)#Photonics|bandwidth]] achievable is a specification of the UV spectrophotometer, and it characterizes how [[monochromatic]] the incident light can be. If this bandwidth is comparable to (or more than) the [[spectral linewidth|width]] of the absorption peak of the sample component, then the measured extinction coefficient will not be accurate. In reference measurements, the instrument bandwidth (bandwidth of the incident light) is kept below the width of the spectral peaks. When a test material is being measured, the bandwidth of the incident light should also be sufficiently narrow. Reducing the spectral bandwidth reduces the energy passed to the detector and will, therefore, require a longer measurement time to achieve the same signal to noise ratio.