Color grating dispersion

Color Plate 13 Grating Dispersion (Section 18-2) Visible spectrum produced by a grating inside a spectrophotometer. 

COLOR PLATE 17 Grating Dispersion (Section 19-1) Visible spectrum produced by grating inside spectrophotometer. 

The radiation from the flash is passed through a Bausch Lomb 500-mm monochromator equipped with a 1200-grooves per mm grating. The linear dispersion is 16.5 A/mm in the first order. Additional colored glass or interference filters can be used in conjunction with the monochromator to... 

Color Plate 23 Polychromator for Inductively Coupled Plasma Atomic Emission Spectrometer with One Detector for Each Element (Section 21-4) Light emitted by a sample in the plasma enters the polychromator at the right and is dispersed into its component wavelengths by grating at the bottom of the diagram. Each different emission wavelength (shown schematically by colored lines) is diffracted at a different angle and directed to a different photomultiplier detector on the focal curve. Each detector sees only one preselected element, and all elements are measured simultaneously. [Courtesy TJA Solutions, Franklin, MA.J... 

A spectroscope is an instrument used to disperse a beam of electromagnetic radiation into its component waves. Many spectroscopes have diffraction gratings that separate the waves, which are beamed to a mirror and reflected back to the eye of an observer. Each wave appears as a separate colored line. 

Fig. 8.3. Ultrashort optical pulses can be shaped by adjusting the phase and amplitude of each spectral component [27]. In the device, the input pulse is incident on a grating that disperses the different colors in different directions, as shown in the figure. The colors are collimated and focused by a lens or mirror. A second similar arrangement in reverse reconstitutes the pulse by redirecting the colors to another grating. At the mutual focal plane of the two lenses, the spectrum of the input pulse is completely resolved so that each spatial location corresponds to a single frequency (or a narrow band). By inserting at this plane a material that causes variations in the phase of each resolved frequency, one can construct a pulse of arbitrary shape, constrained only by the spatial resolution of the arrangement.

A monochromator consists of a dispersion element, an entrance slit and an exit slit, plus lenses and mirrors for coUimating and focusing the beam of radiation. The function of the dispersion element is to spread out in space, or disperse, the radiation faffing on it according to wavelength. The two most common types of dispersion elements are prisms and gratings. You are probably already familiar with the abUity of a prism to disperse white fight into a rainbow of its component colors. 

Inductively coupled plasma atomic emission is more versatile than atomic absorption because emission does not require a lamp for each element. An element emits light at many characteristic frequencies. As many as 70 elements can be measured with simultaneous measurement of emission from each different element. In Color Plate 21, atomic emission entering from the top right is dispersed in the vertical plane by a prism and in the horizontal plane by a grating. The radiation forms a two-dimensional pattern that lands on a semiconductor detector similar to that in a digital camera. Each pixel receives a different wavelength and therefore responds to a different element. 

The authors are grateful to Prof. Amanda Murphy for suggesting this method. It is best to prepare the jar at least one day in advance of class period to allow the iodine to disperse evenly throughout the silica gel. The silica gel should be evenly stained with iodine. When the mixture is first prepared, the silica gel will appear pink, but it will turn to a rusty orange color over time. 

Diode array technology is another leading candidate for measuring color, as well as other visible properties, of specimens. Polychromatic hght reflected or transmitted from a specimen is dispersed by a grating and focused on an array of detectors, each detecting a specific wavelength interval (38) (Fig. 3). Instrument examples of this are Zeiss OFT 311, OFR 311, and MCS 2 x 511 (Fig. 4). 

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