Chapter 7, Problem 7.1QAP

Interpretation Introduction

Interpretation:

The reason for the variation in the slit width of prism monochromator to obtain the constant effective bandwidth needs to be explained.

Concept introduction:

Monochromators are optical devices which transmit a wide range of available wavelengths, a mechanically selectable narrow wavelength band. These could be wavelengths of light or any other radiation.

Answer to Problem 7.1QAP

Over a certain spectral range, the output wavelength is continuously variable in case of prism monochromator and so, the slit width also must be varied.

Explanation of Solution

The wavelength, that is the output keeps changing continuously for a considerable spectral range in case of a prism monochromator while in case of a grating monochromator, the output wavelength remains same, as the radiation is dispersed in the component wavelength.

As the output wavelength keeps varying, the slit width is also required to be varied in case of a prism monochromator in order to keep the effective wavelength constant which is not needed in case of a grating monochromator.

Conclusion

Slit width must be varied to get constant effective wavelength in case of prism monochromator while it is almost same in case of grating monochromator.