Question

Most modern instruments now use a _______ as a dispersing element in the monochromator.

(a) Prism monochromators

(b) Holographic gratings

(c) Diffraction gratings

(d) Replica gratings

This question was posed to me in examination.

My question is taken from Methods of Monitoring Foetal Heart Rate in division Foetal Monitoring Instruments of Biomedical Instrumentation

Answer 1

Right option is (c) Diffraction gratings

The best I can explain: Most modern instruments now use a diffraction grating as a dispersing element in the monochromator, as prisms in general have a poorer stray light performance and require complex precision cams to give a linear wavelength scale. Replica gratings can even be produced more cheaply than prisms and require only a simple sine bar mechanism for the wavelength scale.