In the study of Optical Behaviour of Materials, spectroscopic instruments are used for irradiation of samples as well as for analyzing emitted radiation. Many of these instruments use prisms or gratings as dispersing components. There are a few basic types of these instruments utilizing the above dispersing components. Again depending on the region, these instruments use either plane gratings or concave gratings. Generally speaking, plane grating instruments are used above 2000 A, whereas concave grating instruments are used in the vacuum ultra violet region. Many of these instruments have ingenious scanning mechanisms to display the wavelength or the wave number linearly. The present article tries to review some of the basic principles of these instruments as well as recent progress in this field.