Examples showing the effect of signal averaging on a spectrum’s signal-to-noise ratio. From top to bottom: spectrum for a single scan; average spectrum after four scans; and average spectrum after adding 16 […]
Several of the posts in the Analytical Image and Video Exchange include schematic diagrams of spectrophotometers. Gathered here are jpeg files for the various components used to create these schematic diagrams. source […]
The illustration here shows a schematic diagram of a diode array spectrophotometer, in which we replace a single photomultiplier detector with an array of photodiodes. The source radiation passes through the sample and is […]
The illustration below shows a diagram of a scanning, double-beam spectrophotometer. A chopper directs the source’s radiation, using a transparent window to pass radiation to the sample and a mirror to reflect […]
The illustration here shows a diagram of a single-beam spectrophotometer that uses a monochromator to select the wavelength. The analyst manually selects the wavelength by adjusting the wavelength dial. Battery-operated, hand-held single-beam spectrophotometers […]
The illustration below is a diagram of a simple filter photometer, which uses an absorption filter (shown here) or interference filter to isolate a band of radiation. The analyst either inserts a removable filter […]
Beer’s law suggests that a calibration curve is a straight line with a y-intercept of zero and a slope of εb. In many cases a calibration curve deviates from this ideal behavior, as […]
Absorbance is the more common unit for expressing the attenuation of radiation because it is a linear function of the analyte’s concentration. When monochromatic electromagnetic radiation passes through an infinitesimally thin layer of […]
As light passes through a sample, its power decreases as some of it is absorbed. This attenuation of radiation is described quantitatively T = PT/Po where T is transmittance and PT and Po are, […]
The energy of ultraviolet and visible electromagnetic radiation is sufficient to cause a change in an atom’s valence electron configuration. Sodium, for example, has a single valence electron in its 3s atomic […]
The illustration here shows two electronic energy levels (E0 and E1), each with five vibrational energy levels (ν0–ν4). Absorption of ultraviolet and visible radiation leads to a change in the analyte’s electronic energy […]
A photomultiplier contains a photosensitive surface that absorbs radiation in the ultraviolet, visible, or near IR, producing an electrical current proportional to the number of photons reaching the photomultiplier. As shown here, […]
