An orthogonal-dispersion PGD was investigated in theory. The ray-tracing simulations by ZEMAX indicated the accuracy of the theoretical analysis and mathematical formulas. In order to improve the spectral resolution, the dispersive power of the PGD needs to be improved, which can be realized by either appropriately increasing the vertex angle of the prism, properly reducing the groove spacing of grating, or both. In addition, the dispersive power of the PGD can also be changed by choosing different materials of the prism and grating. There are two main features to the PGD. First, the orthogonal-dispersion PGD is based on the transmission grating, whereas traditional cross-dispersion systems are based on the reflection grating. Second, the transmission grating is superimposed on the hypotenuse surface of an optical wedge with a right-angle surface directly attached to the prism, which not only makes the PGD compact, but also makes the air-glass interfaces fewer and therefore makes the reflection loss less. The unique design makes the PGD capable of providing a compact, small-sized and broadband orthogonal-dispersion device that is applicable to the medium resolution spectrometers.

Question 20.

Discuss the experiment to determine the wavelength of monochromatic light using diffraction grating.

Answer:

Experiment to determine the wavelength of monochromatic light:

The wavelength of a spectral line can be very accurately determined with the help of a diffraction grating and a spectrometer. Initially all the preliminary adjustments of the spectrometer are made. The slit of collimator is illuminated by a monochromatic light, whose wavelength is to be determined. The telescope is brought in line with collimator to view the image of the slit. The given plane transmission grating is then mounted on the prism table with its plane perpendicular to the incident beam of light coming from the collimator.

Dispersive Power Of Prism Experiment Pdf Download