Prisms resolving power

Plot X against n and hence obtain the resolving power of a fused quartz prism, wifh a base length of 3.40 cm, at 200 nm, 250 nm, 300 nm and 350 nm. What is the resolution, in nanometres, at these wavelengths How would the resolving power and resolution be affected, quantitatively, by using two such prisms in tandem ... 

Figure 9. Predicted resolving power for CMOS equipped with the gratings described in Table 1 and slit width 0,5 arcsec. Those prefixed by X are hypothetical immersed gratings with prism vertex angle, (j>, given in the Table 1. The dots mark the nominal blaze condition. The box marks the requirements for measuring the velocity dispersion of dSph galaxies using the Calcium triplet.

Thus, dispersion of the grating increases as d decreases (i.e., as the grating contains more lines per cm). Also, dispersion is not a function of k, and the linear dispersion is therefore a constant, unlike in the case of a prism. The resolving power of a diffraction grating is proportional to the size of the grating and the order of the diffraction used. 

The besl isolation of radiant energy can he achieved with flame spectrometers that incorporate either a prism sir grating monochromator, those with prisms having variable gauged entrance and exii slits. Both these spectrometers provide a continuous selection of wavelengths with resolving power sufficient lo separate completely most of the easily excited emission lines, and afford freedom from scattered radiation sufficient lo minimize interferences. Fused silica or quartz optical components are necessary to permit measurements in Ihe ultraviolet portion of the spectrum below 350 nanometers Sec also Analysis (Chemical) Atomic Spectroscopy Photometers and Spectra Instruments. 

Prism monochromators made of quartz have the great disadvantage of not being very useful below about 2500 A. As one goes to shorter wavelengths the transparency decreases and with it the resolving power. Much quartz also fluoresces in its own right. 

Eqs. 3.1-19 and 3.1-25, which describe the relation between the characteristics of gratings and prisms and the theoretical resolving power Ro, give the optical conductance of grating and prism spectrometers. We may write... 

Resolution of a Prism. The resolving power of a prism is given by... 

The experimental technique involves the use of a high-resolution instrument, one with better resolving power than the usual sodium chloride prism instrument. The solvent commonly used is carbon tetrachloride (sometimes carbon disulfide), both of which have practically no absorption in the 3300 cm region. Amino alcohols cannot be studied in these solvents, however, since they slowly react with the solvents. Tetra-chloroethylene is quite suitable for these compounds, since they are stable in it for extended periods at room temperature. 

The resolving power of a grating has the same dimensions as for a prism and use i again made of the Rayleigh criterion for resolution. The numerical value of the resolving power is given by X/AX, where AX meets the Rayleigh definition. 

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